Cueball

I was having the same problem after upgrading Ubuntu from 8.10 to 9.04, and again from 9.04 to 9.10. I think it's a PulseAudio error, not Express Scribe. First time round a reinstallation of the software fixed it, second time round going to Options>Playback and changing the Sound Device from Default to the specific hardware channel you want to use sorted it out. Hope that helps.