Not sure if it will help, but before you try deleting and reinstalling, go to your AH2/Settings folder. Rename ahvoc.cfg and then try running the game. You will then probably have to set your voice prefs again...
FYI, here's my ahvoc.cfg contents:
0,UseWaveIn
0,RangeChannelBeeps
0,TuneChannelBeeps
1.00,MicVolume
1.00,SpeakerVolume
0.18,EfffectVolume