Volume control (sliders or keys) stops working after plugging into/out of headphone jack

I plug my machine into a projector/sound amplification setup regularly for teaching. Often, when I get back home afterwards, the sound volume controls no longer work. Neither the dedicated volume keys in the function key row, nor the volume slider in the menu bar have any affect on output volume. Also, the keys changes don't affect the slider position, or vice versa.

I've done some searching and testing and the only working solution I've found is to reboot. Not a great solution. I've tried switching output devices (no change) and restarting coreaudio (no change). I'm on 10.6.8.

Any non-reboot suggestions?

Solution 1:

According to this thread, holding down any of the volume keys as you plug or unplug the audio jack will solve this problem. It's a known issue.

See this thread: http://forums.macrumors.com/showthread.php?t=1254855