Why does Exchange 2000 Server Instant Messaging (IM) incorrectly display the status of our IM users?
Occasionally, an IM client's contact list stops accurately reporting the status of one or more users whose IM accounts reside on other servers. This problem can occur if the Jet database that stores the map of IM servers becomes corrupted. Such corruption prevents your IM server from contacting the IM servers of other users on your contact list, which prevents your IM server from accurately tracking the presence of those users.
To force a rebuild of the node database, stop the IM service, delete the files in the \program files\exchsrvr\imdata folder, then restart the IM service. As soon as the next client attempts to log on, the IM service will rebuild the node map, which should correct the problem.