Mumble "windows xp pentium 3" Questions

windows XP system. I here the voice from the other side but not able to open my mumble client window to communicate. I need to restart mumble in such scenario. Can any one provide any solution to such

...windows xp(pro),1gb ram, intel pentium dual cpu e1280@2ghz, with a trial version of bullguard antivirus.... 1st it used to give some proxy settings warning and all that stuff but now after i ...