Party screwing with my soundcard

My soundcard is nothing fancy, just part of Intel chipset on my MB, but I've never had problems with it before.

When I play on Party, the sound will start out okay then gradually get quieter and quieter until I have to crank the volume all the way to hear anything at all.

If I reboot, everything goes back to normal. Then, over time....

This is with only Internet Explorer running in the background, and no non-Party sounds at all.

Anyone experience anything like this before?