It turns out, at least in my case, that the problem was the sound card driver. I had to use an older version of the driver for the soundcard. After downgrading the driver, it works fine.
To get the older version of the driver (if you have the same soundcard that I do), go to Dell support and navigate through to the soundcard drivers for the Dimension 8250. You will probably need to force this driver on your soundcard as, at least for me, using the Dell installer didn't actually downgrade the driver. Extract the files from the Dell package, then go through the standard "upgrade driver" procedure for your soundcard (start->control panel->system->device manage->etc.) and point the driver procedure to the directory made by the Dell installer.