OK, thanks guys, but I have just discovered it's not a Litestep problem (unless Litestep keeps a part of itself in memory while other users are logged on), because when I tried to hibernate with the LiteStep profile logged off and an explorer.exe profile logged on, the same error occurred (and I did install some other programs on the day I installed Litestep...)
So, I have three questions/requests:
1) Does Litestep keep a part of itself in memory while other users are logged on?
2) If not...
2a) Does anyone know of a tool that will help me find out which program is grabbing the keyboard? (Unfortunately, I've forgotten what other programs I'd installed on the day)
2b) Could you please move this post to the offtopic forum (it does not have anything to do with litestep anymore...)

Thank you