Have GMS 2.01 running and have a few users on it. Some are working fine,
but others are not getting connected when doing a synch over the air.
Getting the Trouble Communication over Network error. The device can
connect to the GMS server through a browser window and LOGIN there, but not
connect through the SYNCH operation.

Other similar devices with what appears to be exactly the same settings work

Any ideas on how to further troubleshoot, or factors that could be causing

All synching through a cradle and PC goes OK.