System.InvalidOperationException: There is an error in XML document (0, 0).

[endymion1818]

Thanks @TheDreadPirate, I checked all XML files with an online validator and there were no errors ...

I wonder if it's system.xml that's the issue:

System.InvalidOperationException: There is an error in XML document (0, 0).
---> System.Xml.XmlException: Root element is missing.

But I wouldn't know what was the problem there.