So, whether this is pretty much a common thing I can't say, but it is in my world.
With my old setup, both in Vista and in 7 (both 64-bit), enabling SLI would cause the drivers crash. Typically, reinstalling the drivers and a reboot (or vice versa) took care of the issue and away we went. This was on an XFX 780i board. I'm now on an Asus P6X58D and I can't for the life of me get SLI to work. It's the same scenario in that the drivers crash, but a re-installation or reboot or any combination of doesn't do it. I am running the latest BIOS on this board and the latest drivers as of this post. These are 8800GTs. One EVGA and one BFG.
I did a search and only came up with a few threads, but generally to X58 boards, not this one in particular, so I don't know how much help I can get on this particular issue, but any and all suggestions at this point are more than welcome.
The nVidia forums aren't getting me anywhere so hopefully more knowledgeable folks lurk here.
If for some reason more information is needed, lemme know.
You know what I had the same problem till I switched the GPU's slots. I have a M2N32-SLI Vista Prem board I also have 2 8800GTS's one is EVGA an the other is from BFG. I have the faster of the two in the lower slot for Phyx/SLI. I've done the overclocking bit too and it still didnt work. But now that I have a newer BIOS update I can put ether one in which ever slot I want. but I choose to use the faster one as the added SLI/Phyx. Oh if you can see about using Windows XP 64bit its the greatest. I have Vista 64 and Windows 7 64.
Yeah, try switching the cards to see if that helps. If not, then you may want to try an older driver. Since the 8800GTs are discontinued, nVidia hasn't been too keen on providing fixes for them. Seems like newer versions of the driver introduce more issues than they fix for older 8800 series cards. Try using the same driver version you used on your 780i build.
Heh...that's the same thing I was thinking this morning, but didn't have time to try before work. That's the first thing I'm going to do when I get home. I'm going to assume that it will address the issue.
As far as the driver, I had used the same driver, which was 195.62 or whatever the previous available version was and it was fine.