Serial port problem

Hi
I am having problems finding the serial port I need. I have an Arduino Duemilenove. My computer is a Mac desktop.
The computer only shows the 4 Bluetooth serial ports. It used to work perfectly.

Bad USB cable? Duemilanove uses FT232 for USB/Serial interface, they're usually pretty durable (compared to Atmega16U2 on Uno/Mega).
Have you applied any high voltages to the board recently?