I received this error on a web part page that used the SQL Server Reporting Services native web parts for Report Browsing and report Viewing. Every time I attempted to "connect" the Viewer control to the Browser, I was kicked out to an error page with the following error message:
An unexpected error has occurred.
Web Parts Maintenance Page: If you have permission, you can use this page to temporarily close Web Parts or remove personal settings. For more information, contact your site administrator.
Troubleshoot issues with Windows SharePoint Services.
You may receive an error with a SharePoint page that has other web parts. The immediate fix is to delete the web part, but that's not a real workaround. Changing the trust level for the site worked for me.
This is the complete fix:
1. Open web.config file of current web application
2. Find the node that begins <trust level=
3. Change the trust level from WSS_Minimal to WSS_Medium
4. Save the file
5. Drop to command prompt and execute : iisreset
