Well If I was betting I would say you may have some file permission errors. Meaning the file/directory structure is not set correctly per the installation guidelines.
But to save you time and heartache it may be best to follow Scott's suggestion and just open a support ticket.
There was a small php test script to check for compatibility some where in the purchase area but I can't seem to find it anymore. Maybe it was overlooked when the site moved.
Last edited by Ruben; 01/28/2010 6:56 PM. Reason: Added comment