This is crap. I haven't been able to see my iPhone in iTunes for a few weeks now. Not too bad as I've not needed to put anything on there recently, but now I do want to put some TV on there, oh and OS4 as well. Any clues?
Have you tried anything in terms of troubleshooting already?
First off try a reset on the iPhone. Hold the on/off button and the home button at the same time. Keep holding them and ignore the side to turn off bar. The iPhone screen should go blank, and you can release the buttons. It should reboot.