At some point in the last week, my pulseaudio stopped producing noise altogether. Instead, it complains about constant underruns. I'll attach a log produced with rhythmbox, but flash shows the same problem.
Created attachment 338576 [details] pulseaudio -vvv output
It turns out my system was configured to use digital output for some reason. Switching it back to analog made sound work again. That still doesn't explain why digital output gets instant underruns, but I am going to close this bug for now.