I purchased a Kindle fire for my wife last christmas. It has not been charging although I have purchased a new charger and cord from Staples. It looks like that it is the charging port on the kindle that is bad.
Many people have this problem. I had the same problem and emailed customer service, but before I used their suggestion I used a different charger at work and it charged fine. My charger at home didn't give a full charge even after being plugged in overnight, and at work it took a couple of hours. Customer support did mention a software update, so I would try contacting them.
The issue is with the non-Kindle charger. 3rd party charges WILL charge your Kindle, but don't provide enough power to charge it WHILE you're using it. I discovered this myself, and now I only charge it with the Kindle charger.