Burned Arduino Mega 2560

Whoops, when connecting a Lipo Battery (12.5V) to my way too complicated breadboard (with voltage regulator circuits), I now see that this directly connected to the GND and 5V pins of an Arduino Mega 2560, after 5 seconds and a lot of smoke, I disconnected and now it's broken :(.

When I now power the Arduino the normal way, the RX and TX LED's are constantly on (as well as the ON LED). Does anyone have some pointers as to where to try and replace components? Or is all lost?

Thanks for any suggestions.

If the RX and TX LED's are ON constantly it could be the FT232RL has been damaged as well. I would first remove the ATmega2560 from the board to make sure that is not causing the problem indirectly.

Apart from the FT232, my guess is nothing else was damaged (mostly because there isn't much left to damage!) I would remove the ATmega2560, see if the RX/TX LED's go off and you can at least plug the board in to the USB port and have it show up as a serial port. If so, replace the ATmega2560 and you should be OK. Otherwise, replace the FT232 as well.

The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, light sensor, potentiometers, pushbuttons

Thanks, I am not using the USB port at all (programming via ICSP header), so I'll remove that chip first when I get home. I am not sure if I am ready to remove a 100 pin SMD chip already, as I have never soldered/desoldered SMDs before, on the other hard, there is nothing to break anymore :). I'll be posting my results here.