[TYPO3] Fatal error on update to 4.1.1

[Mads M. Hansen]

Hello, I have just changed distro and in the process restored my site
from backup, the origan site was running on Typo3 4.0.2 and I copied
the dirs over to a 4.1.1 installation. When I login to the BE I get a
warning to run the update wizzard, but when I try to login to the
install tool I get this error:

Fatal error: Cannot redeclare user_mimetype_sniffer() (previously
declared in /srv/eccentric/www/public_html/typo3conf/temp_CACHED_psddac_ext_localconf.php:357)
in /srv/eccentric/www/public_html/typo3conf/temp_CACHED_psddac_ext_localconf.php
on line 367

Any help on this would be greatly apperciated.

.. Mads