Volume Keys Problem

Hey all,
Longtime lurker, first post - never had an issue I couldn't fix by just reading up on it before...

So my volume keys (F10/F11) stop working after I unplug my headphones. I've seen similar issues addressed in forums, but not like this, and none of the suggested remedies seem to help.

On startup, the volume keys work. When I plug in headphones, they continue to work. When I unplug the headphones, they continue displaying the volume icon onscreen, and the volume indicator dots/slider still moves, with no effect on the actual volume. When I plug the headphones back in, same thing: onscreen indicator - no actual change.

Here's what I've tried so far:
•Updating software
•Permissions repair
•Chucking system audio Plist (com.apple.audio.AggregateDevices)
•Resetting PRAM and NVRAM
•Resetting the SMC

I'm running 10.6.8 an iMac from '08.

Any suggestions would be MOST welcome. This thing is driving me bonkers.
THANKS in advance!

I would guess, the Headphone Jack has developed a fault. The jack talks to the software, switching it in the Preferences, so if its crashing the volume software that would explain your symptom.

Have you tried manually toggling the Sound > Output to Internal Speakers before removing the Jack?