There are different 'modes' of sleep, and settings for them, probably the ones in the BIOS got whacked. Check out the ACPI settings, it's going to be different on every motherboard so I can't tell you exactly what to expect, but set them in a way that appears to make sense, then run windows and shut it down instead of hibernate so it can boot for real and figure out that something has changed. then test it. if that doesn't work, install updated motherboard drivers. If that doesn't work, update the BIOS (you never want to do this as a first step because you risk bricking the whole board or causing exactly the sort of fluky windows problems you're experiencing).