I live in Europe and own a Zune 30. A couple of days ago the audio from my zune started dropping out on my left channel. It seemed to come back when I pressed on certain spots on case (never stable results though).
I was able to repair it (sending it to Microsoft from Europe wasn't an option).
MAKE SURE IT ISN'T THE HEADPHONE: Test different headphones out that you know are working before you attempt this solution.
FIX:
1) open up the zune (only removing the backplate)
2) turn it on and play a song (be careful not to touch any of the electronics)
3) press down on points on the headphone jack and listen to the music
4) when pressing down on a certain point does this help the problem?
5) try and figure out where that point is on the backplate (for me it was the bottom half of the headphone jack: so on the backplate that would be between the horizontal plastic mound and the smaller vertical mound)
6) append something that would press down on the jack to the backplate(I cut of the end of a cigarette filter and used a gluestick to keep it in place so I could close it up)
7) close it up
Zune has been working great for a couple of hours now.
PS: only do this if you're sure it's the audiojack and using the warranty isn't an option.
EDIT:
I'm glad to learn that this fix has helped some of you.
This fix worked me for a couple of months, but after a while it started to revert to it's previous problems of one channel falling out.
At this point what seems to really help was putting a needle in between the audio jack and the metal just above the battery. I cut the needle and wedged it in between. It just seems to work after that.
I'd like to know where exactly the problem seems to come up on these old zunes. Maybe I'm forcing something that shouldn't be that much of a problem.
Right now, that needle and some cork on the top seems to help. But I'd like to know what exactly is causing this to make the zune work again.
After this it seems to be stable for the most part.
Let me know how it works for you guys.
EDIT 2:
I found another point that helps with the problem:
The first two spots on the zune, I have discussed above. Number 1 is on the edge of the headphone jack itself. At number 2 you can slightly make out the needle I wedged in. Number 3 is a new spot that comprises of two tiny chips with "GJ8Z" on them. Press on them and for some reason I don't need the two others.
None of the solutions seem very permanent though. I keep my zune unscrewed so I can fidget with it when the left channel keeps dropping out.
EDIT 3:
I think
Talbott has found the best way of fixing this issue. I'm trying his solution out at the moment by sticking some copper wire to some tape and placing it so it connects those GJ8Z chips with the connector directly under the headphone jack.

Sorry about the image quality. My webcam doesn't support macroshooting.
Suddenly everything is working perfectly. This solution isn't permanent though, sometimes the tape doesn't quite hold the wire in place. So I'll be looking in to soldering after I've tested this for a couple of months. As soon as I'm sure that this is the best way of getting rid of the problem, I'll cleanup this guide.
Anyway credit where credit is due: thanks a lot
Talbott. I never quite had the balls for messing about with electronics for fear of some kind of short circuit and bricking the Zune.