I know this may sound like a "Don't you think I would have thought of that.." but.. what were the last driver changes, or hardware additions you did if any?
If no changes at all recently, you could try Loading BIOS defaults, set the section that says OS PNP to NO. Those are some quick things to try.
If you recently were in your system moving cards around.. put them back to the way they were.. or.. reset them all and in different places...
The problem is most likely a driver, but can be caused by a hardware issue too, not necessarily bad hardware, but something just not right.. Like bios setting, etc.