Comment 4 for bug 342578

Ok guys, sorry for the noise. It was indeed this stupid Zend code thing which was once installed on this server (and got not cleanly uninstalled later on), this thread points to the solution:

http://ubuntuforums.org/showthread.php?t=876252

I guess one cannot do anything on Debian's / Ubuntu's side to issue a warning, but hey, at least you're now aware of the issue ;)

Thanks again for your time,
Thomas.