Arduino Won't Connect After Battery Incident

I'm using an arduino mega. I have had the board for a while without any problems. My current project is to convert a 27 Mhz rc car into a wifi controlled car that accepts inputs from my computer. I got as far as a rough prototype where the mega could use the asynclabs wishield. It takes a lot of effort and manipulation to get it all working, but i had it working very well. I was trying to change how i was powering the mega board.

I had a 7.2V nicd battery connected to a 2.1 mm power connector and then plugged it into the arduino. That worked fine and i was able to verify that it was all working correctly. Then i decided to try and use the same 7.2V battery for both the car supply and the arduino. I stopped using the 2.1 mm adapter tip and used the Vin whole instead. I'm not sure what went wrong, but the board started getting extremely hot and smoking before i could unplug it. After that I can't get the board to connect to my computer. The board doesn't even show up as being connected to my computer. (I have an apple macbook pro and i've tried both windows 7, and mac os x 10.6.2 neither one can detect the board.)

I've tried connecting the arduino to the battery using the 2.1 mm tip again to see if i just burned out the FTDI chip, but the program doesn't run anymore. The board seems to be pretty inoperative. When i have the board and the board alone connected through usb it will turn on the power light and the green led, but it isn't detected. When i connect the 7.2V battery through the 2.1 mm tip the voltage regulator next to the DC jack starts warming up, and the FTDI chip gets pretty warm too. I'm not sure what i fried, and if there is an easy way to replace the damaged piece.

Any ideas?

Im pretty sure your going to need to just buy a replacement board. :-/

I don't know why putting something through the VIN header would fry the board, as I'm 99.9% sure that runs through the Regulator too..

Someone before has tried removing the chip (on a Duemilanove), and then running a jumper from TX to RX, sending commands via the serial window, and seeing what comes back. You could try this, but I'm pretty sure that person's board was being recognized, and it also wasn't a Mega (but hey, you could give it a shot).

If you get the message back, it probably means the chip is fried, but even that's not necessarily good, because you'd still need to desolder and resolder a new one in its place. I don't know if you have any experience with SMD soldering, but I hear it's pretty darn difficult if you're new to it.

Good luck!