[TYPO3-install] t3skin lost after server migration from TYPO3 4.0 to 4.0

[Christoph Roth]

Hello,

due to new server hardware we had to make backups from several TYPO3 4.0 
installations (one source tree) and re-install them on a new webserver 
with a fresh 4.0-source tree (4.0 and 4.0 should be identical?).

On the old server, the websites were all running correctly in TYPO3 4.0 
mode with the new t3skin. On the new server, the new skin doesn't load - 
although the extension manager claims that it is "loaded and running" 
which is definitely not the case. All other things seem to work correctly.

I deinstalled the skin extension and installed (activated) it again, but 
no success.

This is very strage. Did anyone have this problem before or knows some hint?

Thank you very much in advance,

Christoph