by Christoph Ruda.
Brian's suggestion sounds plausible. If your Moodle 2.5 is on a different site you need to update the links in your database to point to your new location. There is an easier way to that though. In your Moodle 2.5 installation go to yoursite/admin/tool/replace/index.php and update your database from there. Worked very well indeed for us.
All the best
Christoph
