HELP!!! Nothing will upload to Mega 2560

So I've had a pretty good time uploading firmware to the arduino so far but today when I was planning on changing the steps per mm on the extruder, I never got that far cause I could never upload. Here is the error arduino gave me:

avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: ser_send(): write error: sorry no info avail
avrdude: stk500_send(): failed to send command to serial port
avrdude: ser_recv(): read error: The handle is invalid.

So I need to know why my laptop won't recognize the Arduino.
I've scoured the internet for answers, but didn't find anything. Any help would be greatly appreciated.

The RS-232 chip on the Arduino board may be cooked. Try plugging the board into a different computer...

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

you may need to restore bootloader

[www.avr-developers.com]

Installing an Arduino Bootloader
[learn.sparkfun.com]

Fixed a few days ago. Turns out pronterface was blocking the port.