Why won't XP hibernate suddenly?

I know that Steam interferes, so I always turn it off when I leave the machine downloading something. But that’s not it this time. The only thing I know has changed is that I installed iTunes. Is there some service I need to shut off?

iPodService polls for a connected iPod. If you don’t have an iPod, you could kill that.

I’m having the same problem lately. The only thing I changed was adding a wireless keyboard/mouse, so perhaps that can do it too.

You can fiddle with the keyboard/mouse driver’s power state setting to make hibernate work again. MSDN explanation of s0 s1 s2 s3 s4 s5 states. Hint: you will need to disallow your mouse from waking up your system…something like that.
Random software that diagnoses these problem. I haven’t run that software before, I just found it from goggle for this post!

Bottom line is that XP’s hibernation feature is not very well implemented. It’s a crapshoot: works great for some; sucks for others.