iPhone won't charge and displays "charging not supported by this device"

I've got the same problem, I've just booked into see a genius

Obviously the problem is in your iphone, i think in electric connection, so you can't do anything without assistance with this.

An update. I went in to see a genius and typically my phone charged fine, both with their leads and my leads that I took in.

It's charged ok for the last 2 days but it's now back to saying "charging not supported".

It says this if I charge through the supplied mains lead or an through an official dock connector plugged into any USB port of 3 different PC's I've tried it on.

Any ideas?

Same issue here.

and an FM transmitter that until recently would charge the phone.

You mean, the cigarette port in your car? I think if you try to charge it there, it will say that message, considering that it runs on 12V and the iPhone only requires 5V. I could be mistaken though.

I think you have a problem with the iPhone. Its suppose to charge on a computer because the USB ports on Macs and PCs are only limited to 5V. Bring it to a Apple Store and get it fixed by someone there.

You can actually get a charger for cigerette lighters, has a thing in it drops the voltage down.