This is just further confirming that there is a server error coming from php, it does not give any of the details of the php error itself. In order to troubleshoot the problem we will need a specific php error to work with. Normally when you add in the error reporting code to the top of the page and test it you should see any php errors. What browsers have you tested this in? It would be a good test to try this in another browser to see if you get the same result or a more detailed error message.
If you cannot get past this then you will need to contact your host to see if they can allow errors to be reported directly by the scripts rather than be handled.