Well - there is another problem. It happened also to me: the screen turning blank. My provider blamed skype:
see: http://forum.skype.com/index.php?showtopic=101149
But to me that did not make sense, since I always have skype open. The most recent change I made on my computer was installing ICQ. But I cannot see any relation between that and my problem.
The theme change did not fix my problem. Instead of checking all the sourcecode, I finally wiped off WP totally and reinstalled.
I think somewhere is a real bug - but I cannot solve it.
How could skype unasked make changes that destroy a whole site?
By the way: I use PLESKas backoffice.
One more suggestion: maybe skype or other programms can write to the sql file and change settings??? Trough what app?
Can it be a bug in the theme clean-home that I used?