joadard did you happen to solve your problem? Because I have exactly the same. Also under Plesk, though that’s probably not the cause.
I’ll keep you informed if I find something as well.
EDIT: Setting ALL files permission to 777 didn’t work for me. Anyway having the files world writable wasn’t really viable was it.
I contacted my host Kreativmedia.ch to see if he knows something about this issue. “safe-php” is turned on for me. Heard turning it off solved the problem for some users, but I read somewhere on www.ads-software.com that “safe-php on” wasn’t an issue to run wp.
Let’s see.
