iPhone help!? This is really strange...?

I have an iPhone and I have the same problems as you.

Here is what happened to me: We give our daughter the phone to play with on occasion and she has slobbered on it and caused parts of it to not work (the best that we can hypothesize).

When I play music on youtube or through the iPod, nothing comes out, but when I plug in headphones or use it in the car, it works fine. Also, I hear the ringtone play.

I get the same airplane mode message (and OMG it's so annoying).

SOLUTION:
Go to an Apple store and get a replacement. I hope you are still under warranty, and if you are they should replace it for free. I called 1-800-MY-APPLE. This is what the representative told me to do and said that since I am under warranty still that I can get a replacement for free. Don't go to the AT&T store because there is nothing that they can do (I tried that). They ran some trouble-shooting over the phone. The representative wanted me to restart the phone, which I had already done plenty of times. He wanted me to do a system restore by plugging it into iTunes, but I had already done that before as well.

There is no way to get rid of the airplane mode message. I have had it come and go on both the iPhone 3G and the late model. I know and have felt your frustrations and have tried everything possible! This is the only solution: replacement.