BAD XML in Joomla

I am getting this error,
ErrorType:LoadXML Description: Incorrect XML
when I switch on Debug I get
Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, and inform them of the time the error occurred, and anything you might have done that may have caused the error.
More information about this error may be available in the server error log.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

Such kind of error can appear , when detailed error reporting is disabled on php level. ( it can be that php used in safe mode, and some common extensions are disabled or limited in functionality )