I just received my FC5970 from Performance PCs yesterday. Thought I am not new to watercooling by any means, I still followed the instructions carefully. After I got the loop filled and bled, I fired up the system and booted into Windows (x64 Ultimate). After about 5-10 minutes, I started noticing flickering on the screen, then got the gray vertical stripes (never had that before with this card). Since then I have had several lockups, even with uninstalling the drivers and installing the latest hotfix. Even locks up in the BIOS. This only happened after I changed the stock cooler out for the waterblock.

Anyone have any suggestions? I'm going to have to take the block off and see if something's not making contact right. Damn tight loop though