Sounds like you have a hardware problem preventing the software on your computer from seeing what is on the camera card. You might want to try a different cable, or a card reader, or maybe even putting the camera card into a different camera.
This will not help with your immediate problem, but ultimately you will be much happier using a card reader instead of directly connecting your camera to the computer.
The card readers are faster in the transfer, less error prone, require no special drivers, and do not drain your camera battery.
Another thought might be to try recovery software on the camera card (in a card reader).
The battery failure might have corrupted the camera card and the file data.
I have successfully used the freeware program "Recuva" to restore images on a card formatted by the camera.