Volume problems

[aqpr]

I can't change the volume with the keyboard or the volume bar. It is constantly at top volume and I can only change the output volume from system preferences - sound. Even when I'm using headpones the volume cannot be changed.
Please help!
Thanks

 

[billbaloney]

So what do you see when you look at the Output pane in System Preferences->Sound? Does it have the default settings, like this?

 

[aqpr]

It looks pretty much like that only the output volume is messed up when I try to change it. Also, the sound works fine with headphones now but it didn't before.