I don't see anything immediately obvious. After the firmware update, have you done a BIOS reset to factory defaults, and pulled the AC for twenty seconds? That can clear up some of the weirder problems.
You can also try dropping down to just one DIMM, and run that as a test.
How often are you getting the reboot? Once a day, or once a week, on average?
Yes, I have reset the BIOS to factory defaults a few time and removed power. The reboot occurs at various times which makes it hard to figure out. I did a test a few weeks back right after swapping the motherboard. I created a script to copy a 800GB file to the RAID 1 array, delete and then start over while at the same time running prime95 and loading the CPU to 100%. It ran this script for over a week without rebooting. I thought that perhaps the problem was fixed with the motherboard swap, but after disabling the script and stopping the CPU load on a Friday afternoon, the server rebooted twice over the weekend. I starting thinking about it and checked the properties of the onboard NICs. I disabled all the power efficiency, low power, reduce link speed in standby, etc. and since then the server has not rebooted. What got me to look in this direction was the fact that when copying files across the network continously the server did not reboot for over a week. Anyway, it's been 9 days since disabling those options and so far no reboot. I'm really hoping this solves the issue but time will tell. BTW, I am using Intel Proset 22.214.171.124 in case anyone else has this problem. I will post back here after more testing to confirm this solved the problem. If anyone else has seen this or has any more ideas, please post and let me know.