Looks like I have the same problem when my Macbook Pro boots up linked to my Thunderbolt...
I've noticed that my Thunderbolt sometimes refuses to produce sound and when checking in System Preferences>Sound everything is 'greyed' out from Sound Effects to Display Audio, with a blank where usually there is a Device For Output.
I also had to literally open Finder from the Dock to make it visual on Thunderbolt and some Desktop icons where invisible.
On Restarting the Macbook everything reverted back to what it should be.
The only reason I found for these problems was sometimes when my OSX Lion Macbook was booted it took ages to open, with a progression bar visible, and even longer to open Thunderbolt.
Other times is booted fast with no progession bar and straight to Thunderbolt. No problems.
Will there be some kind of patch/software update I wonder?
I have this problem too. Everything was working fine for the last 4-5 months until recently.
The audio will suddenly switch to "internal speaker" and system preference no longer have the option to switch back to "Display Audio". Restart or unplug/plug back in nothing helps. Thunderbolt display firmware shows no device is detected, which normallly shows the display's status.
I called apple care and they gave a solution, which worked for me somehow. But problems will still come up randomly now, so I have to repeat the steps. Very annoying. I hope apple would release a update or sth to fix this issue once for all.
Here are the steps they gave to reset your display.
1. Shut Down your laptop
2. Unplug Display(both power and thunderbolt connection) for 15 sec or so
3. Press & Release Shift+Control+Option+Power
4. Wait for 15 sec or so
5. Plug back display and power
This trick works for me. But I hate to do it every time this problem comes up, which seems the only way for me to get display audio back to work. Again, I hope they will update the thunderbolt display firmware or do something to fix this issue.
I have exactly the same problem! After reading this thread, I followed the procedure to get it back up working.
Unfortunately, as you've also pointed out, this doesn't solve the problem once and for all. The display seems to drop out fairly frequently, especially after I leave my Air (mid 2011) to sleep.
Rather than pushing Shift+Control+Option+Power everytime, I decided to simply unplug the thunderbolt connection and plug it back in. This seems to work at times, though not a great way to solve the underlying problem.
This is, indeed, extremely annoying. This may be the fisrt time that I realised the Apple ecosystem isn't that harmonious afterall.
FIX REQUIRED ASAP APPLE!!!
I have found another soluton / problem....
Try this, when you notice that the sound does not work, see if any USB devices attached to the display work also... printers etc?
I noticed that when the sound was not working, my Iphone that was plugged into the display was not charging.
1. Leave display powered up but just disconnect thunderbolt cable from computer
2. You will hear a noise from the iphone as it now starts to charge
3. Plus the thunderbolt cable backinto the macbook
4. The iphone may stop charging for a a few seconds but it will start charging again AND the sound will be back.
5. No restarting of macbook required.
I only noticed this as I have a printer attached via usb to the display and wondered why it was not being displayed as been online when it clearly was. Not sure if it will work with other USB devices if you don't have an iphone though.
Same problem -- no sound from monitor speaker when Mac air is attached through thunderbolt cable, and my phone does not charge when plugged in. I also have same experience as Weicheng28 in that unplugging and replugging does not always work. Often have to do it a number of times. Designer Gav UK's method of booting separately then sleep then plug and wake up does not work for me.
That fix solved all my problems Many thanks
However it doesn't resolved the problem that causes it to happen. "Apple" I hope you are reading this and are working on a fix for it.
So every time the laptop goes to sleep and I wake it up, the only thing that works is to change the screen size on the thunderbolt diplay, then it comes back. I can then use it for what I need it for. However if I need sound, camera or attach USB deives the nI need to do what ryanxie suggested.
I guess I should update my final resolution to this post. I took my air and display to Apple store and worked with staff there at least seven times, because this problem annoys me so much(camera, usb, and sound) and I had no luck fixing it on the fly using other methods. So here is what happened.
As a first round of diagnosis, staff in apple store claims that the port on mac air is broken. It took them a week to have the logic board replaced. Unfortunately, problem remains.
Then they told me this problem is escalated to the engineering level and some engineer from Apple will call me and try to help me to address this issue. Obviously, they acknowledge this as a common defect. I gave it another 3 weeks, got no call.
Resubmitted the request for escalation, no call for another week. Finally, the manager from Apple store decided to swop my mac air with a brand new mac pro, because they claim there is a known issue with mac air working with this display. That is how they deal with this kind of recurring issues with customer, I guess.
After swopping, my display still refuses to work. So they bring a new set of thunderbolt display, and tested with the new mac pro, and it works! So they swopped the display again. For this matter, I'm very pleased with apple's customer service. It does took me a lot of time.
Anyways, my new pro and new display is working so far, just like my air with old display when I first got them. But I don't know if this problem is going to come back... Fortunately, all my devices were still under warranty at that time.
So my suggestion really is to go to apple store and keep bugging them until they have this problem resolved for you, if the problem is replicable. I still think there is a common issue with mac air and this display. As they claimed, switching to pro might help (God knows for how long). In my case, my old display was also defective at that moment because it doesn't work even with a new pro.
Thanks for your suggestion and all the effort ryanxie. It certainly is one way to solve it.
However, I think Apple seriousely need to face this problem and solve it in the next software update. Exchanging an Air to a Pro sure isn't the best solution, especially given how they advertise the display as the Ultimate docking station (Do more with an Air? Really Apple? More like do less with an Air...)
Honestly, if anything, this has gotta be one of the most frustrating docking stations. In addtion to the troubles I mentioned before, the sound, camera, and USBs seemed to drop out minutes after I roboot and had everything back on running. So much for living in the Apple ecosystem...
Update to mine - MBP and Thunderbolt only working by 'sleeping' the laptop then waking it up after plugging in the Thunderbolt cable...The only way to get sound to work through the montor speakers.
I forgot to do this step last week and just plugged and booted - everything works perfectly now!?!?
Without going to Apple for replacements; and pre-latest OSX upgrade.
I'm smiling but confused.
I have a brand new mid-2012 MBA and Thunderbolt Display that I purchased at the same time. I have the same problem described here. I noticed it first when my iPhone was not getting charged, and then discovered that audio was only working through the MBA.
I'll give it a few days ... but I may just return both as I need a setup that just works.