After a database restore, when a client performs an add folder, delete folder, or refresh operation, one of the following errors might occur:
"The delta supplied has a destination revision that is older than the current repository's revision."
"Object Reference not set to an instance of an object"
This is occurring because the local cache has a more recent copy of the repository hierarchy than what is stored on the server. To fix this problem, all clients will need to delete their local cache files as described at: Clear Client Side Cache.
Additional information about the cache can be found here:
http://support.sourcegear.com/viewtopic.php?t=6
FAQ: Errors after restoring a database
Moderator: SourceGear