The Windows Server Update Services (WSUS) console crashes when browsing for updates and displays the following error message:

An unexpected error occurred. 
click reset server node to try to connect to the server again

This can occur if the application cache is corrupted.

To resolve this issue, delete the WSUS application cache from the location below:

C:\Documents and Settings\<user profile>\application data\microsoft\mmc

where user profile is the currently logged in user profile.

source: http://support.microsoft.com/kb/2761925