Same issue (AMD E-350 - 12.04 Precise). After reboot, everything is ok. But, if you take out the HDMI and reconnect it, then the sound settings has no more HDMI audio setting anymore, neither does the sound go through. Although, in PulseAudio Volume Control, you can still see that the audio is detected there for the HDMI module.
In 11.10, everything worked fine.
Same issue (AMD E-350 - 12.04 Precise). After reboot, everything is ok. But, if you take out the HDMI and reconnect it, then the sound settings has no more HDMI audio setting anymore, neither does the sound go through. Although, in PulseAudio Volume Control, you can still see that the audio is detected there for the HDMI module.
In 11.10, everything worked fine.