NoeIDE is correct, SMBus will most likely be taken care of by the motherboard chipset drivers. I would still try to get rid of the nvidia drivers...even if it breaks the video, reinstalling your ATI drivers should fix it...
Were it me, I would uninstall everything nvidia and ATI, use something like cleaner or driverfusion to make sure everything is gone, then reinstall the ATI drivers. But...if it is working good, and you are happy with it, you could also just mark the thread solved and be done with it.
Deek
BTW, sorry it took so long, I'd bet if we started with a driver reinstall, it would have been fixed. We did fix a bunch of other problems so, at least that is a plus.