My volume does not work on my macbook pro and every time I press either volume button a "do not enter" sign pops up... the only way I can get sound from my computer is through my headphone jack...
Have you tried going to system preferences, and then in the second section from the top all the way to the right side select the Sound setting, make sure your volume bar toward the bottom on the screen on the output tab is set to an audible level and that the mute box is not checked off.
hmmm sometimes when you plug your headphones in and remove them the computer doesn't recognize they are gone….have you tried firmly inserting and removing the headphones 5 or 6 times from the jack?
also in the sound section be sure you have for the output source you have internal speakers selected, is it possible you have another audio source connected via usb or firewire?
Yes, I've checked all of the system preferences/sound settings and all of them are set to the correct settings. However, in the preference menu I cannot change the volume bar at all. When I press any of the volume keys on my keyboard nothing changes and the "do not enter" sign appears below the volume bar...
9/10 times that means that it believes the headphones are still plugged in, sometimes people have to do it ten or more times, but as i mentioned earlier, sometimes plugging in the headphones and unplugging them a many times in a row will do the trick and get the light to turn off and u will be fine
The red light in the headphone jack means that the MacBook Pro thinks that an optical audio cable is plugged into the port. Like Vinny says, try unplugging and replugging a headphone plug into the port many times. There is a tiny sensor inside the port that determines whether the port operates in optical or analog mode. Plugging something analog in is supposed to trigger the sensor and restore the analog signal.
I have the same problem, but mine doesn't work with headphones now either. Last sound I used was headphones. Today when I turn computer on I get sound during startup, but then get the "do not enter sign" on volume control and no sound. I looked in System Preferences > Sound and the only option is Digital Out.
You might want to mark Vinny's helpful responses as "Helpful" or even "Solved" That is typically the way the forum works. I am glad you were able to find the help you needed.
Vinny V's suggestion of plugging and unplugging my headset in and out (5 or 6 times) of the audio jack on the side of the computer resolved my problem of the Volume Controls buttons not working on my MacBook Pro running 10.6.3 (I tried so many other things, and this worked? lol)