No sound with live messenger and c-media

I cannot get sounds with Windows Live Messenger 8.5. If I try to configure sounds, I get an error message indicating the speakers are in use by another program. After a while, the sound on all programs fails, and Device Manager indicates that the Microsoft Kernel Wave Mixer driver cannot be loaded. If I restart, sound comes back. Also, sometimes after a lengthy time on, I cannot get any sound in Windows Media Player 11,when playing MP3's. If I restart the computer, I get the sound back.

I am using a C-Media 8738 Audio Card, with updated drivers from August, 2009. Windows XP Pro, SP3, and all updates.

Thanks!!

Dave