I'm running Ubuntu 10.10 on a Revo r3610 nettop with integrated sound (Intel HDA) and graphics (nVidia ION).
When I boot up with the monitor turned on everything works fine. If I then turn off the monitor sound continues to work as normal. However if I boot up with the monitor turned off, I cannot play sound. When I turn on the monitor, it just suspends itself without displaying a picture. If I VNC to the box, the sound icon in the tray shows as muted (three dashes) and nothing is shown in the hardware sound devices panel. The sound card still shows up in an
lspci listing though.
The monitor is connected via HDMI and the sound is via 3.5mm headphone jack to an external amp. The monitor also has integrated speakers but these are not in use.
Edit: I've also noticed that the computer only goes to sleep/suspend when it was booted up with the monitor plugged in. Otherwise it stays on all the time. It seems that some part of gnome is not being started properly when it can't find the monitor.