DV8,
I have had that problem before, and it seemed to occur like every other build, as if something fundamental had changed with every other build, although I don't know what. I'm not having it now, but it did seem to occur only when I used ASIO (using M-Audio Revolution and the M-Audio ASIO drivers). Sometimes a reboot would clear it up, but sometimes not. I don't know that answer and I'm sorry, but you might also try this.
First, update to Win2K Service Pack 4.
Next, go into Control Panel>Sounds and Audio Devices>Hardware (tab) and select your soundcard. Click the "Properties" button. In the "Properties" window that pops up, click the "Properties" tab, then expand the "Audio Devices" node. Select your sound card, then click the "properties" button near the bottom. Check the "Do not map through this device" checkbox so that it is checked. I read somewhere that that helps, and I did it and coincidentally haven't had any more problems (but I also stopped using ASIO too). Maybe that might help.
Wobbley