Hi,
Do you use Office LiveMeeting Services? If yes, does this problem only occur when using LiveMeeting or even out of meeting you cannot hear the audio? If the audio problem just occurred in LiveMeeting session, please follow the steps below to setup audio:
1. On the Live Meeting 2007 toolbar, click Voice & Video to access the Voice & Video pane.
2. Disable and then enable the speaker in the Live Meeting client.
3. In the Voice And Video pane, select Set Up Audio And Video, and then complete the instructions that are presented on the screen.
Hope this helps.
Lu Zou