My iphone isn't recognized by finder or itunes

Hi,

I got an iphone 3gs not too long ago, and everything seemed to be fine. On the rare occasions that I wanted to sync it, I did so successfully. I don't sync often, so I'm not exactly sure when the problem arose, but in any case, now, when I connect my phone to my macbook, nothing happens. It will charge, but it still won't show up on the desktop, or in the finder under devices, or in itunes.

I just tried reinstalling itunes and it still doesn't work. When I plugged the phone into another computer, it recognized it fine. Both computers currently run 10.6.8.

Anyone know how to help me with this?