I brought up the F11 display and sure enough, it was tracking below 100% at times. Most of the time it would hover from 90% to 100%. The pops would definitely get worse when momentarily it would drop to around 60%.

I'm running Ubuntu on a core i5 2.67G x 4, should that be able to keep up?

Unfortunately, the on board sound doesn't work under ubuntu, so I've got a USB audio adapter and I wonder if that contributes to any slowdowns.

Thanks for the -sl4 "" tip, that empties out the Mockingboard.