Did you have all peripherals disconnected & the AC power disconeted when you took the battery out?
What to do if your computer won't recognize a FireWire or USB device...
If the issue persists, try these steps:
1. Shut down the computer.
2. Disconnect all devices and all other cables, except the keyboard and mouse cable(s).
3. Disconnect the computer from the power outlet and wait for 3 to 5 minutes.
4. Plug the computer back in and turn it on.
5. Reconnect the device(s) (one at a time if there is more than one) and test. Test with each port if you have more than one.