Mac Pro Freezes when performing certain Tasks?

Question

My Mac pro has been freezing recently which requires me to hard boot and I'm not quite sure whats going on. Let me go a bit more into detail.
Now when I say freeze, I don't mean beach balling, I mean literally the entire screen is motionless and I must hard reboot. Its odd really, the computer only freezing when doing certain tasks, such as when I render 3D graphics with Cinema4D, or whenever I play certain games on steam.
I have recently installed windows as a partition for bootcamp, but I don't believe that is the issue. I have experienced the freezes while running my machine in both Windows and Mac.
Its important to note that when booting my Mac in SAFEMODE, the freezing does not occur while performing the same tasks. So this leads me to believe there is a process going on thats causing the computer to freeze up?
What I think I have managed to rule out as problems:
- Not a Hard Drive failing issue, I booted from my backup hard drive and the freezing still occurs.
- Not a Heat issue, I've installed iStat and my top temperature barely raises to 60 degrees celsius when freezing occurs.
- Not an issue with the Windows partition, as I booted from my backup drive that is without the partition and the freezes still occur.
- Not a Ram issue, I took my ram cards out and swapped them around.
One other things... Not sure if this is relevant, but upon one of the freezes, I rebooted and got this on my startup screen, It was bizaar and it froze here as well. This only occured once but I snapped a photo of it.
Any ideas? Could it be a graphics card issue?
Thank you for your help!
Specs:
Mac Pro (Early 2009)
Hardware Overview:
  Model Name:          Mac Pro
  Model Identifier:          MacPro4,1
  Processor Name:          Quad-Core Intel Xeon
  Processor Speed:          2.26 GHz
  Number Of Processors:          2
  Total Number Of Cores:          8
  L2 Cache (per core):          256 KB
  L3 Cache (per processor):          8 MB
  Memory:          8 GB
  Processor Interconnect Speed:          5.86 GT/s
  ATI Radeon HD 4870:

Answer 1

That panic was not caused by third-party software. If it's a recurring problem, the remaining possibilities are (1) a damaged Mac OS installation; (2) a hardware fault, which could be internal or in a wired peripheral device; and (3) an obscure bug in the Mac OS.
You can rule out the first possibility by reinstalling the Mac OS. Probably there will be no change. In that case, make a "Genius" appointment at an Apple Store to have the machine tested.
Print the first page of the panic report and bring it with you.
Back up all data on the internal drive(s) before you hand over your computer to anyone. If privacy is a concern, erase the data partition(s) with the option to write zeros (do this only if you know how to restore, and you have at least two independent backups.) Don’t erase the Lion recovery partition, if present.