I was troubleshooting another issue on a client’s production server and ran across the following errors in the event log (Application Log). The error was occurring on a KnowledgeLake Viewer web service. After some quick searching I found Namwar Rizvi’s post on how to fix the problem. It appears that SharePoint output caching is trying to access the web service that is called by a web part which is causing the error to occur.
Event Type: Error
Event Source: Office SharePoint Server
Event Category: Publishing Cache
Event ID: 5785
Time: 9:29:56 AM
Unable to connect publishing custom string handler for output caching. IIS Instance Id is ‘50319175’, Url is ‘http://xxxx.com/_layouts/klviewer/WebResource.axd?d=’.
For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.