Sudden system crashes for Mac mini 2011

Question

I just came home from a 2-week vacation and my computer has begun to crash and reboot, seemingly when I need the computer to do some task more intensive than Internet browsing.
It started when I tried uploading pictures into iPhoto via my camera's SD card--and it invariably happens whenever I try this--but it has also crashed and rebooted during simple multitasking procedures, like clicking to check my download progress in Safari as my iPhone is syncing in iTunes. Yesterday I had to contend with the white (grey?) screen of death for a few hours as I tried different methods. Fiddling around in Safe Mode let me fix that problem, at least, but the sudden system crashes still persist.
Could my computer have been affected by a lack of use over the last two weeks in the summer heat? It's been hot in the house, but not exceptionally so for August. And before I left I shut it down and unplugged the power cord.
Here are the first several dozen lines of the error report from the most recent crash. If anyone could offer me some help, I'd be very grateful.
Interval Since Last Panic Report:  72 sec
Panics Since Last Report:          2
Anonymous UUID:                    5966B3C8-D237-441F-B085-67433211CA95
Thu Aug 30 22:31:31 2012
panic(cpu 0 caller 0xffffff800d7733f2): assertion failed: MBUF_IS_COMPOSITE(m), file: /SourceCache/xnu/xnu-2050.9.2/bsd/kern/uipc_mbuf.c, line: 4003
Backtrace (CPU 0), Frame : Return Address
0xffffff80f52f3c20 : 0xffffff800d41d5f6
0xffffff80f52f3c90 : 0xffffff800d7733f2
0xffffff80f52f3ca0 : 0xffffff800d78d2f8
0xffffff80f52f3d60 : 0xffffff800d77075f
0xffffff80f52f3d90 : 0xffffff7f8e264d2e
0xffffff80f52f3dd0 : 0xffffff7f8e280d7b
0xffffff80f52f3e30 : 0xffffff7f8e2f79d4
0xffffff80f52f3ec0 : 0xffffff7f8e26b62f
0xffffff80f52f3ef0 : 0xffffff800d847078
0xffffff80f52f3f30 : 0xffffff800d845b8a
0xffffff80f52f3f80 : 0xffffff800d845cb9
0xffffff80f52f3fb0 : 0xffffff800d4b2677
      Kernel Extensions in backtrace:
         com.apple.driver.AirPort.Brcm4331(601.15.21)[2D12C2AA-EED3-3C72-8A75-FFF39E64DA AC]@0xffffff7f8e25e000->0xffffff7f8e44ffff
            dependency: com.apple.iokit.IOPCIFamily(2.7)[8C9E06A4-13D0-33F5-A377-9E36F0ECC229]@0xffffff 7f8da4d000
            dependency: com.apple.iokit.IO80211Family(500.15)[3CA3EBF7-D5C1-3819-9346-BE648FC7644E]@0xf fffff7f8e1f2000
            dependency: com.apple.iokit.IONetworkingFamily(3.0)[4DB5B398-8957-33F6-9EC1-0D45D80769DD]@0 xffffff7f8db8f000
BSD process name corresponding to current thread: kernel_task
Mac OS version:
12B19
Kernel version:
Darwin Kernel Version 12.1.0: Tue Aug 14 13:29:55 PDT 2012; root:xnu-2050.9.2~1/RELEASE_X86_64
Kernel UUID: 3005059E-270B-3B9F-940D-7A66C05DDC9D
Kernel slide:     0x000000000d200000
Kernel text base: 0xffffff800d400000
System model name: Macmini5,1 (Mac-8ED6AF5B48C039E1)
System uptime in nanoseconds: 2262319547463
last loaded kext at 432629451752: com.apple.driver.AppleUSBCDC          4.1.22 (addr 0xffffff7f8efac000, size 16384)
last unloaded kext at 543566806951: com.apple.driver.AppleUSBCDC          4.1.22 (addr 0xffffff7f8efac000, size 12288)
loaded kexts:
com.zeobit.kext.Firewall          2.3
com.apple.filesystems.msdosfs          1.8
com.apple.driver.AppleHWSensor          1.9.5d0
com.apple.driver.AppleBluetoothMultitouch          75.15
com.apple.driver.AudioAUUC          1.60
com.apple.driver.AGPM          100.12.69
com.apple.driver.ApplePlatformEnabler          2.0.5d4
com.apple.iokit.IOBluetoothSerialManager          4.0.9f8
com.apple.driver.AppleMikeyHIDDriver          122
com.apple.filesystems.autofs          3.0
com.apple.driver.AppleHDA          2.3.0f2
com.apple.driver.AppleMikeyDriver          2.3.0f2
com.apple.iokit.BroadcomBluetoothHCIControllerUSBTransport          4.0.9f8
com.apple.driver.AppleSMCPDRC          1.0.0
com.apple.iokit.IOUserEthernet          1.0.0d1
com.apple.Dont_Steal_Mac_OS_X          7.0.0
com.apple.driver.ApplePolicyControl          3.2.6
com.apple.driver.ACPI_SMC_PlatformPlugin          1.0.0
com.apple.driver.AppleUpstreamUserClient          3.5.10
com.apple.driver.AppleMCCSControl          1.0.33
com.apple.driver.AppleLPC          1.6.0
com.apple.driver.AppleIntelHD3000Graphics          8.0.0
com.apple.driver.AppleIntelSNBGraphicsFB          8.0.0
com.apple.driver.AppleIRController          320.15
com.apple.AppleFSCompression.AppleFSCompressionTypeDataless          1.0.0d1
com.apple.AppleFSCompression.AppleFSCompressionTypeZlib          1.0.0d1

Answer 1

Remove the "MacKeeper" crapware as follows, then reboot and test. If there's no improvement, post again.
Note: These instructions apply to the version of the product that I downloaded and tested in early 2012. I can't be sure that they apply to other versions, nor do I intend to repeat the test.
IMPORTANT: "MacKeeper" has what the developer calls an “encryption” feature. In my tests, I didn't try to verify what this feature really does. If you used it to “encrypt” any of your files, “decrypt” them before you uninstall, or (preferably) restore the files from backups made before they were “encrypted.” As the developer is not trustworthy, you should assume that the "decrypted" files are corrupt unless proven otherwise.
In the Finder, select Go ▹ Applications from the menu bar, or press the key combination shift-command-A. The "MacKeeper" application is in the folder that opens. Quit it if it's running, then drag it to the Trash. A dialog will pop up asking why you want to uninstall it. You don't have to provide that information. Enter anything you like in the text box, then click the Uninstall button. All the functional components of the software will be deleted. That's the only useful feature of "MacKeeper:" it deletes itself. Reboot.
Do not try to uninstall by dragging the MacKeeper icon in the Dock or the LaunchPad to the Trash.
Here are some general suggestions. If you want your computer to be usable, don't install crapware, such as “themes,” "haxies," “add-ons,” “toolbars,” “enhancers," “optimizers,” “accelerators,” “extenders,” “cleaners,” “defragmenters,” “firewalls,” "barriers," “guardians,” “defenders,” “protectors,” most “plugins,” commercial "virus scanners,” "disk tools," or "utilities." With very few exceptions, this kind of material is useless, or worse than useless.
The more actively promoted the product, the more likely it is to be garbage. The most extreme example is the “MacKeeper” scam.
The only software you should install is that which directly enables you to do the things you use a computer for — such as creating, communicating, and playing — and does not modify the way other software works. Never install any third-party software unless you know how to uninstall it.