Module Administration Fatal Error

I get an error on mutiple Trixbox 2.2 installations where FreePBX has been upgraded from 2.3 to 2.4. I do not get this error on all of the upgraded boxes. One box was even fine for a while before this started happening. It happens when I click “Check for updates online”. It is a blank page except for this:

Module Administration
XML error: undefined entity at line 1