Aria always has critically low battery. HELP!!!

[robertito]

I dropped my Aria the other day while shopping with my wife, and now the phone is having problems retaining a charge on the battery. At least that is what appears to be the problem. What happens is the phone always registers the charge on the battery as critically low (2 - 5% charge remaining) even after leaving the phone plugged in overnight. I've rooted the phone so I was able to update the ROM from 2.1 --> 2.2, but it's still doing the same thing. I put a friend's battery that was 50% charged into my phone, and it still registered as critically low. There's clearly a problem with the device itself so I need to go to AT&T to have it replaced under warranty. However, I know that rooting a phone voids the warranty so I have to revert to the non-rooted stock AT&T ROM. I downloaded the ROM update, and installed HTC Sync on my PC. However, the ROM update utility provided by HTC will not update the ROM without 30% battery life. How can I revert my phone to the non-rooted stock AT&T ROM so I can get a new one from AT&T? Also, are the HTC phones typically this sensitive to being dropped? I've had a number of cell phones, and have never had any major problems after dropping them.