I have just upgraded my iPhone 3GS to iOS4. When I plug it in to the Pioneer iPod connector it now says that charging is not supported and no sound is heard. Both symptoms are new.

Also, and more importantly, I cannot seem to pair it with my iPhone (or any other Bluetooth device). It does not see any nearby devices. Any thoughts?

I can only address the BT issues,

My 3G upgraded to 4 and my 4 both pair and work properly for calls.

Mine would no longer pair either. I just deleted the current connection and searched for new devices. It took a while for it to recognise the iphone but it eventually found it and it auto connects now everytime again. I also experienced problems with the audio side of things when i first plugged it in but it seems to work fine now. I get the same message as you but it doesn't affect anything. The problem i find is that searching through artists is incredibly slow, I can no longer search alphabetically and fast forward hardly fast forwards at all.

My iPhone (3G, iOS4) pairs fine, the ipod function does not work anymore... I get an annoying error message that says "ipod failed to connect. please disconnect and try again"...