When your SharePoint 2010 search result Page show the following error:
There are three solutions to solve it:
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.
Hope this helps