Latitude 3330 Battery Not Recognized

Hi--

I have a Latitude 3330 laptop and the computer has stopped recognizing the battery. I assumed it was the battery and bought  a new one, but the problem is still there.

I've already tried:

1) Blowing compressed air over the various connections.

2) Removing the battery, powering it on with only the charger, and then turning it off, giving the machine a chance to use up any residual power. Then I put the battery back in again, and it still doesn't recognize it.

Any thoughts?

Thanks!