I am currently experiencing a very strange issue regarding booting into Windows 7 64-bit (installed on its own 1TB HDD). If I restart my Mac Pro, hold down the option key, and select my Windows partition, I get a black screen and the fans spin up. However, if I completely power down the machine and cold boot it, I am able to hold down the option key and select Windows and boot successfully. So, essentially, I am able to boot into Windows only after a cold boot, and not a restart due to the aforementioned problems.
This same issue occurs even when trying to boot to the Windows 7 installation DVD, so I know it doesn't have anything to do with my Windows installation. Rebooting from Windows to OS X works perfectly. I have tried running the Apple Hardware Test and it detected no issues. I also ran TechTool Deluxe. Any help is greatly appreciated!