Hi Gareth
Gareth, such information is not helpful, a description of the phone status, of which operations has been performed before freeying, may provide a hint. There could be normal reasons. For instance, to avoid "ghost" phones on the PBX (phones which doesn't send authenticated, two-steps unregister requests) 3CXphone waits ~4sec; if connection is tunneled, it additionaly waits ~4sec. During this time, application is not responsive. Also, if tunnel attempts to resolve an invalid address, it waits for system answer, usually ~30 secs, during this time being unresponsive. Obviously, it may be a bug leading to this freezing behavior, but that's exactly why I'm asking for further informations.
However, yesterday we released a patched 3CXphone, fixing three important issues, so I suggest you to try it to see if it performs better than the version you have.
Regards
vali