Comment 6 for bug 134125

Using Gutsy Tribe-5 64-bit I appeared to be suffering this problem, but found an explanation and solution.

1. Open Volume Control
2. Edit > Preferences: select all tracks (including Digital so you can keep an eye on things)
3. On the Switches tab, select Microphone
4. On the Capture tab, ensure the Capture track is enabled and the sliders are up

Keep Volume Control open and visible

5. Start Sound Recorder
6. Choose 'Record from input' "Capture"

Note that the Microphone symbol in Volume Control>Capture tab gets disabled

7. Re-enable the microphone in Volume Control > Capture
8. Start recording

Note that the 'Recording from input' source changes to "Digital" and the microphone symbol in Volume Control>Capture tab gets disabled again.

9. Whilst still recording, re-enable the microphone in Volume Control > Capture
10. Stop recording
11. Playback (you should hear the recorded sound)

It looks like some kind of strange interaction with Sound Recorder and/or Gnome because if I use Audacity, and select "ALSA: HDA ...." as the input source there is no problem with the input switching.