Nagios stopped-Internal Module error

Iam newbie to Univention. The Nagios module was working fine with me. But suddently it stopped and when we start the service it again fails and says the following error.
Internal module error: An error occurred during command processing.

Server error message:

Starting the following services failed: nagios3.
Where should I check for the error? Pls help

I'd check first if the solution from applies.