A good thing to do when you encounter a error-message is to search for it on for example google, often but not always several people have encountered the same problem before.

This is what I found:
https://discussion.dreamhost.com/thread-135829.html

Hope it helps

Since last monday the 16th, the message below appear when you click on the site:

"I MediaWiki internal error.

Exception caught inside exception Handler"
Any idea on what's going on? I've sent a message on the IMPDb forum too, with no answer from anybody for the moment.