When you search in SharePoint 2010, you may get the following error:
Internal server error exception
Troubleshoot issues with Microsoft SharePoint Foundation.
Correlation ID: de2996f1-a6c9-42fb-a6da-e5fc7d769069
*NOTE You will have a different Correlation ID! Look up your Correlation ID in your log files.
You will have to install the following hotfix
For Windows Server 2008 R2, Hotfix for.NET Framework 3.5 SP1 that provides a method to support the token authentication without transport security or message encryption in WCF (http://go.microsoft.com/fwlink/?LinkID=166231).
Reboot your server(s). Ensure that your search services have started.
Ensure you dont have any issues with your search databases. Eg. Out of disk space, SQL Alias not present on all SharePoint servers.