Volume buttons not changing volume??

Hi!

I've got a year-old macbook pro with OS-X 10.6.8.

When I press the volume buttons on my keyboard, the icon shows up and indicates that I'm changing the volume--I hear the "pops" and the levels go up and down--but the volume doesn't actually change...

If I open "sound" in system preferences, I can press the volume buttons and the volume will actually change as the slider goes up and down. The volume I hear after I close system preferences always stays at the same level I left it on in "sound."

And when I plug in headphones, they are always at the loudest possible volume and it doesn't respond to the buttons either. There's no red light showing in the headphone jack.

PLEASE HELP!!!
Thanks!!

These types of problems are very hard to track down.

First I'd boot back into the Admin Account you should have setup when the Mac was new and have never used. See if the problem is in that account too.

I only have one account set up that I know of, but thanks!

I ran AppleJack and all is well (for now) I have no idea what went wrong or how not to accidentally do it again, which is kind of a pain, but at least it works now.

Thanks again!!