Voice is not working in Messenger

I have been using voice and video in Messenger several
weeks without any problem. PC with XP communicating PC
with W2000. Headset (Logitech) and camera (Creative)both
USB connected. Suddenly yesterday didn´t voice work in
any direction butvideo was still working. Headset checked
and is working with Tool Tuning Wizard. What do you
think? Thanks.