I've installed few modx site, never had this problem, with same host and same servers...
With modx 2.2.2 there is also the problem, same server, same configuration... the message is :
syntax error:
Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator,
[email protected] 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.