Late 2013 iMac on OSX 10.9.1 keeps crashing and restarting

Question

My iMac's been crashing lately while using Manga Studio with a Wacom tablet and listening to iTunes, usually after about 40m~1h of using the two programs together. However, I don't believe those programs themselves to be the cause. This is something I do frequently, but these crashes have only started happening about a day ago or so happening about 4 times total by now. I'm thinking it's a software issue, probably a background application, but I can't tell what the offender is. If anybody out there could help me, I'd really appreciate it!
Anonymous UUID:       D85624E1-8D8E-7E2A-12AA-BCBE9CF56CCE
Sat Feb  8 04:50:04 2014
panic(cpu 6 caller 0xffffff800ba54be4): "a freed zone element has been modified: expected 0xffffff8033b7ed00 but found 0xffffff803f84e080, bits changed 0xc330d80, at offset 0 of 128 in zone: kalloc.128"@/SourceCache/xnu/xnu-2422.1.72/osfmk/kern/zalloc.c:461
Backtrace (CPU 6), Frame : Return Address
0xffffff81f5acbbf0 : 0xffffff800ba22f69
0xffffff81f5acbc70 : 0xffffff800ba54be4
0xffffff81f5acbcb0 : 0xffffff800ba5267d
0xffffff81f5acbd10 : 0xffffff800ba51d09
0xffffff81f5acbe10 : 0xffffff800ba2aa2f
0xffffff81f5acbe40 : 0xffffff800bde080d
0xffffff81f5acbe80 : 0xffffff800be202dd
0xffffff81f5acbf60 : 0xffffff800be3db67
0xffffff81f5acbfb0 : 0xffffff800baf3af8
BSD process name corresponding to current thread: Google Chrome He
Mac OS version:
13B42
Kernel version:
Darwin Kernel Version 13.0.0: Thu Sep 19 22:22:27 PDT 2013; root:xnu-2422.1.72~6/RELEASE_X86_64
Kernel UUID: 1D9369E3-D0A5-31B6-8D16-BFFBBB390393
Kernel slide:     0x000000000b800000
Kernel text base: 0xffffff800ba00000
System model name: iMac14,3 (Mac-77EB7D7DAF985301)
System uptime in nanoseconds: 6482418625264
last loaded kext at 11244467619: com.apple.driver.AppleBluetoothHIDKeyboard          170.15 (addr 0xffffff7f8dcf8000, size 24576)
last unloaded kext at 114995240361: com.apple.driver.AppleFileSystemDriver          3.0.1 (addr 0xffffff7f8df6c000, size 8192)
loaded kexts:
com.avg.netshield.kext          1.1
com.Cycling74.driver.Soundflower          1.5.1
com.manycamllc.driver.ManyCamDriver          0.0.9
com.apple.filesystems.msdosfs          1.9
com.apple.driver.AppleHWSensor          1.9.5d0
com.apple.driver.AppleBluetoothMultitouch          80.14
com.apple.filesystems.autofs          3.0
com.apple.filesystems.ntfs          3.11
com.apple.iokit.IOBluetoothSerialManager          4.2.0f6
com.apple.driver.AGPM          100.14.11
com.apple.driver.ApplePlatformEnabler          2.0.9d1
com.apple.driver.X86PlatformShim          1.0.0
com.apple.driver.AppleMikeyHIDDriver          124
com.apple.driver.AppleUpstreamUserClient          3.5.13
com.apple.driver.AudioAUUC          1.60
com.apple.GeForce          8.1.8
com.apple.driver.AppleHDA          2.5.3fc1
com.apple.driver.AppleThunderboltIP          1.0.10
com.apple.driver.AppleMikeyDriver          2.5.3fc1
com.apple.iokit.IOUserEthernet          1.0.0d1
com.apple.iokit.BroadcomBluetoothHostControllerUSBTransport          4.2.0f6
com.apple.Dont_Steal_Mac_OS_X          7.0.0
com.apple.driver.AppleHWAccess          1
com.apple.driver.AppleLPC          1.7.0
com.apple.driver.AppleSMCLMU          2.0.4d1
com.apple.driver.AppleIntelHD5000Graphics          8.1.8
com.apple.driver.AppleIntelFramebufferAzul          8.1.8
com.apple.driver.AppleMCCSControl          1.1.12
com.apple.AppleFSCompression.AppleFSCompressionTypeDataless          1.0.0d1
com.apple.AppleFSCompression.AppleFSCompressionTypeZlib          1.0.0d1
com.apple.BootCache          35
com.apple.driver.AppleUSBHub          650.4.4
com.apple.driver.XsanFilter          404
com.apple.iokit.IOAHCIBlockStorage          2.4.0
com.apple.driver.AppleSDXC          1.4.0
com.apple.iokit.AppleBCM5701Ethernet          3.6.9b9
com.apple.driver.AirPort.Brcm4360          800.21.45
com.apple.driver.AppleAHCIPort          2.9.5
com.apple.driver.AppleUSBXHCI          650.4.3
com.apple.driver.AppleACPIButtons          2.0
com.apple.driver.AppleHPET          1.8
com.apple.driver.AppleRTC          2.0
com.apple.driver.AppleSMBIOS          2.0
com.apple.driver.AppleACPIEC          2.0
com.apple.driver.AppleAPIC          1.7
com.apple.nke.applicationfirewall          153
com.apple.security.quarantine          3
com.apple.driver.AppleBluetoothHIDKeyboard          170.15
com.apple.driver.AppleHIDKeyboard          170.15
com.apple.driver.IOBluetoothHIDDriver          4.2.0f6
com.apple.driver.AppleMultitouchDriver          245.13
com.apple.kext.triggers          1.0
com.apple.iokit.IOSerialFamily          10.0.7
com.apple.iokit.IOAcceleratorFamily          98.7.1
com.apple.nvidia.driver.NVDAGK100Hal          8.1.8
com.apple.nvidia.driver.NVDAResman          8.1.8
com.apple.driver.DspFuncLib          2.5.3fc1
com.apple.vecLib.kext          1.0.0
com.apple.driver.AppleThunderboltEDMSink          1.2.1
com.apple.driver.AppleUSBAudio          2.9.3f17
com.apple.iokit.IOAudioFamily          1.9.4fc11
com.apple.kext.OSvKernDSPLib          1.14
com.apple.iokit.IOBluetoothHostControllerUSBTransport          4.2.0f6
com.apple.iokit.IOBluetoothFamily          4.2.0f6
com.apple.driver.AppleSMBusPCI          1.0.12d1
com.apple.driver.AppleHDAController          2.5.3fc1
com.apple.iokit.IOHDAFamily          2.5.3fc1
com.apple.driver.X86PlatformPlugin          1.0.0
com.apple.driver.AppleSMC          3.1.6d1
com.apple.driver.IOPlatformPluginFamily          5.5.1d27
com.apple.iokit.IOSurface          91
com.apple.iokit.IOAcceleratorFamily2          98.7.1
com.apple.AppleGraphicsDeviceControl          3.4.12
com.apple.iokit.IONDRVSupport          2.3.6
com.apple.driver.AppleSMBusController          1.0.11d1
com.apple.iokit.IOGraphicsFamily          2.3.6
com.apple.iokit.IOUSBHIDDriver          650.4.4
com.apple.driver.AppleUSBMergeNub          650.4.0
com.apple.iokit.IOSCSIBlockCommandsDevice          3.6.0
com.apple.driver.AppleThunderboltDPOutAdapter          2.5.0
com.apple.driver.AppleThunderboltDPInAdapter          2.5.0
com.apple.driver.AppleThunderboltDPAdapterFamily          2.5.0
com.apple.driver.AppleThunderboltPCIDownAdapter          1.4.0
com.apple.iokit.IOUSBMassStorageClass          3.6.0
com.apple.iokit.IOSCSIArchitectureModelFamily          3.6.0
com.apple.driver.AppleUSBComposite          650.4.0
com.apple.driver.CoreStorage          380
com.apple.iokit.IOUSBUserClient          650.4.4
com.apple.driver.AppleThunderboltNHI          1.9.2
com.apple.iokit.IOThunderboltFamily          2.8.5
com.apple.iokit.IOEthernetAVBController          1.0.3b3
com.apple.iokit.IO80211Family          600.34
com.apple.driver.mDNSOffloadUserClient          1.0.1b4
com.apple.iokit.IONetworkingFamily          3.2
com.apple.iokit.IOAHCIFamily          2.6.0
com.apple.iokit.IOUSBFamily          650.4.4
com.apple.driver.AppleEFINVRAM          2.0
com.apple.iokit.IOHIDFamily          2.0.0
com.apple.driver.AppleEFIRuntime          2.0
com.apple.iokit.IOSMBusFamily          1.1
com.apple.security.sandbox          278.10
com.apple.kext.AppleMatch          1.0.0d1
com.apple.security.TMSafetyNet          7
com.apple.driver.AppleKeyStore          2
com.apple.driver.DiskImages          371.1
com.apple.iokit.IOStorageFamily          1.9
com.apple.iokit.IOReportFamily          21
com.apple.driver.AppleFDEKeyStore          28.30
com.apple.driver.AppleACPIPlatform          2.0
com.apple.iokit.IOPCIFamily          2.8
com.apple.iokit.IOACPIFamily          1.4
com.apple.kec.pthread          1
com.apple.kec.corecrypto          1.0
Model: iMac14,3, BootROM IM143.0118.B00, 4 processors, Intel Core i7, 3.1 GHz, 16 GB, SMC 2.17f2
Graphics: NVIDIA GeForce GT 750M, NVIDIA GeForce GT 750M, PCIe, 1024 MB
Memory Module: BANK 0/DIMM0, 8 GB, DDR3, 1600 MHz, 0x80AD, 0x484D54343147533641465238412D50422020
Memory Module: BANK 1/DIMM0, 8 GB, DDR3, 1600 MHz, 0x80AD, 0x484D54343147533641465238412D50422020
AirPort: spairport_wireless_card_type_airport_extreme (0x14E4, 0x111), Broadcom BCM43xx 1.0 (6.30.223.154.45)
Bluetooth: Version 4.2.0f6 12982, 3 services, 23 devices, 1 incoming serial ports
Network Service: Wi-Fi, AirPort, en1
Serial ATA Device: APPLE SSD SD0128F, 121.33 GB
Serial ATA Device: APPLE HDD HTS541010A9E662, 1 TB
USB Device: BRCM20702 Hub
USB Device: Bluetooth USB Host Controller
USB Device: FaceTime HD Camera (Built-in)
USB Device: PTK-640
USB Device: Logitech USB Headset
USB Device: Cruzer
Thunderbolt Bus: iMac, Apple Inc., 23.10

Answer 1

Remove "AVG Internet Security/Antivirus" and see whether there's an improvement.
Any third-party software that doesn't install by drag-and-drop into the Applications folder, and uninstall by drag-and-drop to the Trash, is a system modification.
Whenever you remove system modifications, they must be removed completely, and the only way to do that is to use the uninstallation tool, if any, provided by the developers, or to follow their instructions. If the software has been incompletely removed, you may have to re-download or even reinstall it in order to finish the job.
I never install system modifications myself, and I don't know how to uninstall them. You'll have to do your own research to find that information.
Here are some general guidelines to get you started. Suppose you want to remove something called “BrickMyMac” (a hypothetical example.) First, consult the product's Help menu, if there is one, for instructions. Finding none there, look on the developer's website, say www.brickmymac.com. (That may not be the actual name of the site; if necessary, search the Web for the product name.) If you don’t find anything on the website or in your search, contact the developer. While you're waiting for a response, download BrickMyMac.dmg and open it. There may be an application in there such as “Uninstall BrickMyMac.” If not, open “BrickMyMac.pkg” and look for an Uninstall button.
Back up all data before making any changes.
You will generally have to reboot in order to complete an uninstallation. Until you do that, the uninstallation may have no effect, or unpredictable effects.
If you can’t remove software in any other way, you’ll have to erase and install OS X. Never install any third-party software unless you're sure you know how to uninstall it; otherwise you may create problems that are very hard to solve.
WARNING: Trying to remove complex system modifications by hunting for files by name often will not work and may make the problem worse. The same goes for "utilities" such as "AppCleaner" and the like that purport to remove software.