Inspiron 1526 battery not charging while plugged in....

Inspiron 1526 laptop battery was charging fine for the first 2 months, then all of a sudden, it's not charging. Thought at first it was the AC source, but the computer runs fine while plugged in. Contacted Dell support, they send me a new battery, well same problem. The new battery won't charge at all either. The only way we've been able to use the computer is if it is plugged in. Is anyone else having this problem or does anyone know what the problem could be? Thanks!!