WSOD on add or edit content type.

I get the white screen whenever I add or edit a content type. Typically it does save the changes made, but I have to go back in. Then it stopped saving the changes. I am just restoring to a backup, but I was wondering if anyone has this problem? I'm looking through my code to see if it could be a ?> tag at the end of a file, but I've tried this before and it didn't work.