CATALYST 8.5+ Freezes Vista

Hi. This is my first post here so please be gentle.

After installing only Windows Vista Business 64bit edition on my computer, then if I install any CATALYST version above 8.5, a number of problem occur when restarting after installation:

1. The OS freezes at different points when starting up.
2. The OS and CCC start up fine, but after a random period of time (up to 20 minutes) the OS freezes. The keyboard and mouse are completely unresponsive.
3. Blue screen either at startup or after startup.

The system seems to run fine prior to installing your drivers, but messes up afterward. I've tried the following things to fix it, with no effect:

1. Checked video card seating
2. Switched out my ASUS EAH4850 with another identical one (I intended to crossfire them if I got one to work by itself)
3. Tried the following different CAT versions: 8.5, 8.6, 8.7beta, 4800 series hotfix. All had same effect.
4. Tried installing after installing Vista SP1.
5. I'm about to try to install this with 64-bit XP and see if the problem persists. I will update this with the results.

Here is my system setup:
1. ASUS EAH4850 (Radeon HD4850)
2. GIGABYTE GA-EP45-DS4P LGA 775 Intel P45 ATX Intel Motherboard
3. Intel Core 2 Quad Q9300 Yorkfield 2.5GHz LGA 775 95W Quad-Core Processor Model BX80580Q9300
4. 2xMushkin (2x2GB)DDR2 SDRAM (8GB total)
5. CORSAIR CMPSU-750TX 750W ATX12V / EPS12V Power Supply

Please help. I've been pulling my hair out over this for the better part of the week.