Hey - i have the following Problem with my TS3 Client ( 3.0.8 ) a few Weeks now

whenever i use my Headset ( Senheiser PC350 ) outside of TS3 the Sound Playback Volume is fine - as soon as i switch into TS3 and try to communicate or even testing my Settings inside Options-Playback the Volume is nearly muted - i adjusted my Volume Lvls to maximum ( Headset ,TS3 and System ) and i am barely able to hear a whisper from it.
I am running it on Windows 7 ( auto patched ) with an MSI 770 G45 Mainboard and VIA HD Onboard Sound.
all other Stuff like Games ,Music and Movies is running over my Asus Xonor D1 Soundcard and not affected in any Way by TS3.( Soundcard is set to Standard Device for Playback ,Onboard is set as Standard Communications Device )

Any Suggestions how to fix the Soundproblem within TS3 ?