I've got 2 GTX 460s in SLI right now. My PSU is 750 W, and I've got a Gigabyte ud3r-x58a motherboard, with 6 GB Ram, an i7 930, and a couple hard drives.
The thing is, sometimes, when I boot up into windows, my display is on extremely low resolution. I'm connecting to a 23" 1980x1080 display, but my cards only put out 800x600. Sometimes they go full resolution, but when they don't, the device manager says that Windows stopped them from working because they reported a problem.
When I try the cards individually, they work fine. It seems the cards themselves are not defective.
Could the problem be because of a defective motherboard, or is the PSU providing problems? Perhaps it's a defective SLI Bridge?
I'm baffled, because they worked perfectly for about a month in SLI, and their performance was fantastic. I got Metro 2033 on Very High settings DX11 working at about 45 fps.
I came across your post as I'm having the exact same issue as you. I have the same MB and dual Gigabyte GTX460's. Only difference is this issue started for me when I added an add'l 6GB of ram to my system for a total of 12gb. Once I removed the add'l ram or one of the vid cards, everything works fine.
I am still unsure as to why this problem came up. Recently, I noticed that the low resolution only occurred when I had one or more devices plugged into a USB port. Specifically the front panel USB port which attaches to the motherboard. I have no idea if this is what is really causing the problem or how a USB device plugged in could possibly cause this problem, but I have stopped booting up with USB devices plugged in, and I have had no low resolution problems. Hope this helps.