ActiveSync 4.0 USB Connection Problems.

Problem:
In some specific cases, Windows Mobile device connectivity to a Windows PC running Microsoft ActiveSync 4.0 may experience connection problems. For example, the connection is never established between the PC and the mobile device, or the connection is dropped during data transfer or synchronization, or only partially completes, etc. This appears to be a problem only with the 4.x versions of ActiveSync, not the 3.x versions.
Solution:
Connection problems can be caused by desktop firewall applications or applications that manage network traffic. These applications can conflict with the TCP traffic between a Device and the PC. Firewalls that may cause problems include Norton, McAfee, Trend Micro, Sygate and Zone Alarm.

For detailed instructions on how to configure these firewalls or other applications to allow ActiveSync traffic, see:

http://forums.msexchange.org/m_1800452353/mpage_1/key_/tm.htm#1800452353