I'm not sure on this but you may need to turn off the blue tooth thingie ( tech speak) for the computer cable to connect.
The computer in on cable and the phone is on bluetooth, they cant connect.
This is just a think ......
My computer will not recognize connection to my Blackberry Storm. I have installed the software & using the USB provided with the phone. It seems to have stopped working after I paired the Bluetooth in my vehicle with my phone. Please help.
Bluetooth being on shouldn't effect the connection, You don't say if your computer is on all the time, I would try re-booting your computer and it should refresh the USB.