Microsoft have created a Trouble Shooting Guide for Activesync 4
In some specific cases, Windows Mobile device connectivity to a Windows PC running Microsoft ActiveSync 4.0 may experience connection problems. This document will describe the known issues, and how you may resolve these issues.
*Please note that it is recommended that customers use ActiveSync 4.0 only for devices running Windows Mobile 5.0 software.
Issues:
The end users experiences include the following:
Connection between a Device and PC is dropped during data transfer or synchronization.
Connection is never established between PC and the Device and there is no visual feedback.
Synchronization is completed partially, but does not finish as intended.
The PC does not function
For more information visit:
http://www.microsoft.com/windowsmobi...c/default.mspx