I will add my voice to the mix and maybe help with the troubleshooting. I am experiencing a number of scenarios between two "dock" devices and two different Apple devices. I have a Sony iHome ( i think that is the name) at work and a Bose Sound Dock at home. I have a iPhone 4 and a iPod Touch recent version with camera etc. Both Apple devices worked flawlessly with both playback docks prior to my updating to iOS 5 (music and charging). I don't think I even was warned as others have been about compatability issues.
After iOS 5 I the status is as follows:
Sony iHome dock:- Niether the iPhone nor the Touch will playback music. They both however will charge when connected. Interestingly with the iPhone if I tip the angle while it is seated with the connector on the dock - I can get it to intermittently playback through the speakers as it should. This would have normally told me that there was an issue with the connection but the fact that it all happened at once and is happening on other docks is too bizzarre to be explained away that easily.
Bose Sounddock:
iPhone iOS 5.0 seems to work well - charges and plays back. iPod Touch however played for a while - then stopped working, then started, then now has stopped all together. I have updated the Touch in hopes that I would have the success that others have had but it has not helped. Still no playback - however it does now register as being able to charge when in the dock.
Also i have connected to the audio input jack and both devices playback fine through that.
So while I am no expert, my testing seems to indicate that something in the recent updates has caused the playback through the bottome port to become very undependable if it works at all.
I will try to reset and restore to factor default - (hopefully an old OS) on my ipod touch and see what happens.
I will report back. In the mean time I look forward to hearing what tricks others have tried.
Thanks ,
Scott