Power management stopped working as configured [solved]

I've resolved the following issue but thought I'd post about it anyway in case someone else get the same problem.

After having used my Aspire One 150 with Windows XP PRO for a few months with no problems the power management suddenly was screwed up yesterday. For some unknown reason the power button stopped reacting and even though I configured my power management to do nothing when the lid was closed, the computer still went to suspend mode. No changes to the power management made any difference. It kept doing what I felt was the Windows XP default behaviour.

Tonight I just tried to deactivate the support for hibernation, and then activate it again, by toggling the checkbox in Control panel->Power management->Hibernation (I think that's correct. I don't have an English version so it's a bit of a guess). This solved the issue! Now the power button reacts and power management works as I have configured it.