no Serial Ports detected

I was testing my Arduino Duemilanove at controlling a buzzer and it suddenly stopped working. The Arduino was not able to be detected over serial. I assumed the chip had somehow been fried, so I switched it out for another ATMega328 with arduino bootloader preloaded. However I found when plugging into my computer, there is still no serial port detected. All serial ports were grayed out in the Arduino software. My computer still works with other Arduino's. Any idea on how to get this board working?

When plugged in, does the FTDI chip get warm? It is what communicates with your PC, not the ATmega328.

You might also check the 3v3 line, since it is generated by the FTDI.

No parts appear to get especially warm. I imagine they're already fried. The 3.3 V line seems to output 5V though. Would soldering on a new FTDI chip probably solve the problem? Although the pins are pretty small, so this could be a challenge.

The 3.3 V line seems to output 5V though.

Sounds like it is shot.

Would soldering on a new FTDI chip probably solve the problem

Probably.

so this could be a challenge.

More of a challenge than you think. Getting the old one off without destroying the board would be the hardest part. You probably need a hot air gun.