One question:
Do you run a sound server like arts, esd, jack or similar?
If not, then it\'s not a miracle that you don\'t hear TeamSpeak as Planeshift is blocking the sound device/sound card.
There are some soundcards who can do sound mixing themselves, but not too many of the normal consumer cards. So you either find one of those or you use a sound server or a plug-in like dmix for alsa.
So for me this looks like a Linux-only issue ...