audio jack showing red light indicator

Insert a headphone plug into the port and gently wiggle it around in there, mainly in the horizontal plane. The analog/digital switch in the port has become stuck in the digital position, a fairly common minor problem. Doing as I've suggested will usually unstick it. Repeat as needed.

Sound output is stuck in digital mode.

Plug the headphone into and out of the socket couple of times to flip the microswitch.

Reset SMC.

http://support.apple.com/kb/HT3964

Choose the method for:

"Resetting SMC on portables with a battery you should not remove on your own".

Hope this helps.

Try System Preferences>Flash>Advanced tab>Delete All...

My wife's 2011 mbp had the same problem:

no sound from speakers,

sound okay in headphones,

red light on in jack,

slow computer.

She plays MANY different FLASH online games in Firefox. I searched everywhere and found the same advice as you all did ref toothpick in headphone jack, etc. Nothing worked.

Today, I googled "firefox" "problem" and "sound". I found "Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems". I stopped reading at this point and decided to check out the status of her Flash settings. I opened System Preferences > Flash and explored the different tabs and options on my mbp compared to hers and noticed a LOT more "websites" in her Storage and Camera & Mic tabs. I went to her Advanced tab and selected Delete All... . It took over a minute to clear all her "websites". I did a reboot and was shocked, surprised, relieved that her mbp speakers were spewing sounds again! Problem solved! Her computer is now faster as well.

Short story:

System Preferences>Flash>Advanced tab>Delete All...

Hope it works for you, too.

Hi.

I've recently had a similar problem with my MacBook Pro (mid 2012). The most common solution to this problem i have found was to wiggle either a toothpick or the like in the audio jack, this did not solve anything in my case. What I later find out (and I hope this I'snt the case with your laptop) is that the actual logicboard (motherboard) is damaged and needs replacing which was the case for me.

Hellow. I have the same problem on macbook pro 13 (mid 2010). Truobble was in bootcamp 4.0. Delete bootcamp 4.0 and install ver. 3.1. from you MAC OS install DVD. It slove my problem.