I had this issue when I tried to sync at work. It seems this is an issue with WM5 and firewall settings. At my workplace they run Sygate, but I think there is a problem with other firewall apps as well. As near as I can figure, WM5 uses tcp/ip functionality when using the USB port to sync with the cradle. This is different than ActiveSync 3.8. The microsoft bone heads really created a ball buster this time. Certain firewalls do not take favorable to this process. Microsoft has an item in the knowledge base and if you peruse through aximsite you will find this topic covered already.
MS site is:
http://www.microsoft.com/windowsmobi...c/default.mspx
I personally never implemented the suggested fixes, but rather switched to syncing using infrared which is not affected by this issue. I heard bluetooth syncing is also not affected.
Hope this helps.