Security Update causing system crashing??

Question

Hey everyone.  I installed the latest Security Update last night, and my computer hasn't been acting right since.  After being on for about 20 minutes or so, the screeens go to black, but the computer itself seems to still be on.  There doesn't seem to be any power going to the keyboard though because the caps lock button doesn't light up when I push it.  It's been going on all day, and I'm hoping maybe somone out there can shed some light on it for me.  It'd be much appreciated!  Here's the details of the crash....
I'm running 10.8.4 on an early 2008 8 core Mac Pro
Interval Since Last Panic Report:  1743393 sec
Panics Since Last Report:          2
Anonymous UUID:                    7F25451C-BF94-B6B3-A617-1459B5DA0D24
Sat Jul 20 13:27:13 2013
Machine-check capabilities 0x0000000000000806:
family: 6 model: 23 stepping: 6 microcode: 1547
Intel(R) Xeon(R) CPU           E5462  @ 2.80GHz
6 error-reporting banks
threshold-based error status present
Processor 0: machine-check status 0x0000000000000005:
restart IP valid
machine-check in progress
MCA error-reporting registers:
IA32_MC0_STATUS(0x401): 0x1000000020000000 invalid
IA32_MC1_STATUS(0x405): 0x0000000000000000 invalid
IA32_MC2_STATUS(0x409): 0x0000000000000000 invalid
IA32_MC3_STATUS(0x40d): 0x0020000000000000 invalid
IA32_MC4_STATUS(0x411): 0x0000000000000011 invalid
IA32_MC5_STATUS(0x415): 0xb200001084200e0f valid
  MCA error code:            0x0e0f
  Model specific error code: 0x8420
  Other information:         0x00000010
  Threshold-based status:    Undefined
  Status bits:
   Processor context corrupt
   Error enabled
   Uncorrected error
Processor 1: machine-check status 0x0000000000000005:
restart IP valid
machine-check in progress
MCA error-reporting registers:
IA32_MC0_STATUS(0x401): 0x1000000020000000 invalid
IA32_MC1_STATUS(0x405): 0x0000000000000000 invalid
IA32_MC2_STATUS(0x409): 0x0000000000000000 invalid
IA32_MC3_STATUS(0x40d): 0x0020000000000000 invalid
IA32_MC4_STATUS(0x411): 0x0000000000000011 invalid
IA32_MC5_STATUS(0x415): 0xb200001080200e0f valid
  MCA error code:            0x0e0f
  Model specific error code: 0x8020
  Other information:         0x00000010
  Threshold-based status:    Undefined
  Status bits:
   Processor context corrupt
   Error enabled
   Uncorrected error
Processor 2: machine-check status 0x0000000000000005:
restart IP valid
machine-check in progress
MCA error-reporting registers:
IA32_MC0_STATUS(0x401): 0x1000000020000000 invalid
IA32_MC1_STATUS(0x
Model: MacPro3,1, BootROM MP31.006C.B05, 8 processors, Quad-Core Intel Xeon, 2.8 GHz, 12 GB, SMC 1.25f4
Graphics: ATI Radeon HD 2600 XT, ATI Radeon HD 2600, PCIe, 256 MB
Memory Module: DIMM Riser B/DIMM 1, 1 GB, DDR2 FB-DIMM, 800 MHz, 0x80AD, 0x48594D5035313241373243503844332D5335
Memory Module: DIMM Riser B/DIMM 2, 1 GB, DDR2 FB-DIMM, 800 MHz, 0x80AD, 0x48594D5035313241373243503844332D5335
Memory Module: DIMM Riser A/DIMM 1, 4 GB, DDR2 FB-DIMM, 800 MHz, 0x02BA, 0x202020202020202020202020202020202020
Memory Module: DIMM Riser A/DIMM 2, 4 GB, DDR2 FB-DIMM, 800 MHz, 0x02BA, 0x202020202020202020202020202020202020
Memory Module: DIMM Riser A/DIMM 3, 1 GB, DDR2 FB-DIMM, 800 MHz, 0x80AD, 0x48594D5035313241373243503844332D5335
Memory Module: DIMM Riser A/DIMM 4, 1 GB, DDR2 FB-DIMM, 800 MHz, 0x80AD, 0x48594D5035313241373243503844332D5335
Bluetooth: Version 4.1.4f2 12041, 2 service, 18 devices, 1 incoming serial ports
Network Service: Ethernet 1, Ethernet, en0
PCI Card: Intensity Pro, sppci_video, Slot-2
PCI Card: ATI Radeon HD 2600, sppci_displaycontroller, Slot-1
Serial ATA Device: WDC WD3200AAJS-41VWA0, 320.07 GB
Serial ATA Device: ST2000DM001-1CH164, 2 TB
Parallel ATA Device: OPTIARC DVD RW AD-7170A
USB Device: Keyboard Hub, apple_vendor_id, 0x1006, 0xfd400000 / 2
USB Device: USB Optical Mouse, 0x046d  (Logitech Inc.), 0xc06c, 0xfd430000 / 4
USB Device: Apple Keyboard, apple_vendor_id, 0x0220, 0xfd420000 / 3
USB Device: Bluetooth USB Host Controller, apple_vendor_id, 0x8206, 0x5d200000 / 3
USB Device: iLok, 0x088e, 0x5036, 0x5d100000 / 2
USB Device: FaderPort, 0x194f, 0x0201, 0x3d100000 / 2
FireWire Device: built-in_hub, 800mbit_speed
FireWire Device: 003Rack, Digidesign, 400mbit_speed

Answer 1

That machine check with uncorrected error is almost always a RAM memory problem. Your report does not call out the specific module(s) involved.
Sometimes this information can be found if you look in the About This Mac > (More Info) > Memory system report. like this one:
If modules "drop out" they can generate an error message in the diagnostic pane. Do you have modules in Riser B DIMM 3 & 4 ?? If so, they have dropped out.
If you remove the side door after the failure, sometimes the failed modules will have the Red LED lit up next to them.