As mentioned here: https://discussions.apple.com/message/18057392#18057392 I'm posting this to help others. Now I'll try it myself and come back later.
Found another thread where a solution is offered.
I used to use Personal Hotspot on my iPhone with USB in order to not to drain my battery. But now it seems my iPhone doesn't get found by my MacBook Pro. I've got Mac OS X Snow Leopard. This problem occurred since I installed something like DiskAid or some tool to 'browse' the iPhone like iPhone...
