One day while I was trying to upload code to drive an LCD to my UNO, it wasn't working. So I checked to make sure I didn't accidentally have the wrong board or serial port selected, and it turns out that the serial port I used was gone, and so were others! I'm using OS X and so the serial port I used was /dev/tty.usbmodem621 or something like that. Now my Arduino sketchbook is telling me that the only available serial ports are /dev/tty.Bluetooth-PDA-Synch, /dev/cu.Bluetooth-PDA-Synch, /dev/tty.Bluetooth-Modem, and /dev/cu.Bluetooth-Modem. Can anyone explain to me why I'm having this issue or how to fix it? Thanks.
Sorry, I fixed it myself. Turns out the ATMega chip was partially out of its socket... Kind of embarrassing actually that I spent days updating my drivers, reinstalling the Arduino IDE, and browsing help forums... but now I know what could be the issue if this ever happens again!