How do you start YateServer?
If you go to a Terminal and issue the "ps -Aaf | grep yate" command, what results do you get?
Does issuing "telnet 127.0.0.1 5038" command int the Terminal work?
Do you see any log message regarding Yate (starting or crashing) in the Console? If so, please post them here. Also, please look in ~/Library/Log/CrashReporter if you have any logs for Yate crashing and if so, please post them here.