Pro Mini not communicating with computer
You did set the Serial Port and then tell the Arduino IDE that it's talking to a Pro Mini right?

This gets me every time I switch between my Nano &amp; Uno.

On the main menu
[Tools]->[Board]=>"Arduino Pro or Pro Mini (5V, 16 MHz) w/ ATmega 328"

I've also had this problem trying to use a longer USB cable, it just wouldn't work.  The stock cable (shorter) worked fine.