Hi Kelvin,
Root cause could be a DNS problem, have a look at this post:
http://developer.cisco.com/web/jabber-developer/jabber-voice-forum/-/message_boards/message/5459231In the log file (softphone.log - full path in the post), search for "processNodeName", which is the CUCM address the plugin is trying to connect to. If host name, is it resolvable from the client machine ?
Thomas