Comment 35 for bug 579117

I'm still watching, but I lack both time and ideas. Kubuntu 10.04 does not run pulseaudio so that could be the reason for differences in behavior. (Kubuntu 10.10 will run Pulseaudio, btw.)
That there are no "noise floor calibration timeout"s under kubuntu seems interesting though. I'm not sure what it is that Kubuntu does not do in that case.
This is a case when there is hard to know the real root cause and what messages are just other victims of the latency, it could be that the calibration timeouts are not the real causes.

As for trying different kernels, I think it would be interesting to try linux-preempt (available in Lucid, use Synaptic to get it) and see if it makes a difference.