Printer suddenly stopped working, "could not open port COM3"

My Kittaz has been working flawlessly (aside from my own sloppy calibration issues) for over 6 months now. Now all of a sudden pronterface refuses to connect to the printer. It had just completed a print maybe an hour before - I disconnected it, let it cool off, set up for another print, and that’s when it refused to connect. It gave this error message:

[ERROR] Could not connect to COM3 at baudrate 115200: Serial error: could not open port COM3: [Error 2] The system cannot find the file specified.

A cursory google search suggests the problem might be either a port issue (seems unlikely since I had just been printing an hour before), or the voltage regulator in the Rambo might be fried. The Rambo’s LEDs light up when turned on - I’m not very experienced with electronics, can anyone tell me how to diagnose the source of the problem?

Your USB port may not be com 3 anymore. You can check port assignments from device manager, or just try ports 4 through 9 until it connects. 1 and 2 should be system reserved. If none of them work it could be a hardware issue. Also check any USB hubs.