One of my users having the same issue. Unfortunately I can't access the computer otherwise could have looked at the event viewer to see if gives a hint of why its happening. Bollyviewer check the following and see if you get it to work.
1. Check you Anti-Virus app and make sure that it is not blocking WLW.
2. See if you can add WLW to the list of programs in Firewall exceptions.
also please post in detail, if you find anything in event log
Systems Administrator
MCSE | MCITP - Server 2008 | MCTS - Exchange 2007