I know there are hundreds of posts on this topic but none of the solutions help. Someone here must know.

The problem:
My iphone 3gS 3.1.2 was JB and unlocked with blackra1n last year. I use it with T-Mobile. Have had problems interfacing with computer in the past but managed to fix - usually by cleaning the contacts with rubbing alcohol or it would magically work itself out.

This time is different. I hadn't checked into Cydia for a few months, did so and it updated. Next time I tried to connect iphone to macbook pro, ITunes recognized and started to sync then stopped and wouldn't recognize iphone. I disconnected, then reconnected. Did the same thing. Now it will not recognize the phone.

It is not the USB port or cable because it will recognize my ipod just fine.

It is not the contacts on the iphone because I can charge from the wall and my anaspec iphone adapter in the car.

The other symptom is that when I connect it to my windows machine at work to charge (worked in the past), I now get a USB error message and it will not charge.

SO, it is as if something has changed with the phone such that the computer will not recognize it. Did ITunes banish it?

Any thoughts?