[Mediawiki-l] preview images

[Scheid, Bernhard]

I use version 1.16.2, PHP 5.3.3 (cgi-fcgi), MySQL 5.1.52 for more than a year already. Out of a sudden all attempts to create preview images (no matter whether I use "thumb" or another parameter) result in an error message: "Fehler beim Erstellen des Vorschaubildes," New original files are not affected, but no smaller versions are shown, even on file-pages! Strangely, the same error does not occur on a backup version of the same wiki on the same server. Also, I did not change any settings in  LocalSettings.php. Last time the Wiki worked as it should is only a few days ago.

Any suggestions?
Thank you

Bernhard