This has been a very Apple centric month. I finally upgraded my very first mac, a pre-Aluminium iMac from Tiger to Leopard. The upgrade process was very easy. The next morning, I discovered that my new iPhone is no longer recognized by iTunes ! It worked before the upgrade. The problem only exists with iTunes. When I plug the iPhone into the system, Aperture starts up recognizing the photos. So it seems to be an iTune only problem. A quick search on the Apple support site reveals that this is a known problem. Just download iTunes and reinstall (ever though it is already at the right version) solves the problem.
More info at Apple support discussion group here.