OK, I bet your bottom dollar at one time or another you’ve had this error in your ULS Log when you get an “unknown error” on your SharePoint farm:

That is one of those messages isn’t it.  The one which you look on the internet, and there doesn’t seem to be any answer other than  ‘re-install’ SharePoint.  Well I’m sure that my words here will not cover every situation or eventuality, but hopefully they’ll help somebody. I encountered this recently on a number of separate occasions all relating to different Service Applications.  Here’s the incident’s and the associated solutions: PerformancePoint Designer.  Users were unable to log into the Dashboard Designer, even though they could hours earlier. The above message appeared in the ULS logs.  This was solved by a simple IISRESET across the farm. Search Service.  The search results page stated that it was unable to connect to the Search Service.  The above message appeared in the ULS logs. This was solved by re-booting the Search Servers hosting the Query and Crawl Service Applications. Excel Services.  No workbook would render irrespective of whether it had a data source or which web application it was in.  This was solved by deleting and re-creating the Excel Service Application.  This is no problem, as there is no attendant database associated with excel Services

Hopefully these examples will help somebody somewhere.

Cheers

Dave Mc