>Maybe: http://blogs.technet.com/b/heyscriptingguy/archive/2013/03/05/use-powershell-to-find-certificates-that-are-about-to-expire.aspx
>
>Lots of other variations if you google 'find expiring certificates'

Thanks, I have forwaded that link to the net team with the findings of the Event Viewer. That one triggers every four hours, six times a day. So, there is obviously a certificate somewhere that is either not properly installed or expired. It does not seem to be related to our IIS however as this one has been verified several times and we are supposed to be good until 2017.