Ventrilo Problem

I already asked about this problem before but i think i explained it a bit wrong.

First of all, my ventrilo works completly fine and i usually never have any problems with it. But when playing a game(usually the free MMORPG's) my microphone goes completely mute. The green light does not even show up. I can hear people fine but my button just goes completly dead.

Please help!! i've been trying for a week to fix it and still not even any suggestions.

SoundCard: Turtle Beach Riviera 5.1
OS: Windows XP