I double checked that all my board settings were right (3.3v atmega328 8mhz), and I made sure that I checked "Set RTS on close" in the device manager as specified by the Arduino tutorial for the Pro ...

To fix Arduino upload error, make sure you've selected the right board in the Arduino IDE, remove pins from the board, and reset the board.

I just updated from 1.6.7 and got this error message while uploading my sketch to UNO.

[psgarcha] took a year-old Arduino Uno on an international trip and upon returning found something was wrong. Every time he would try to upload, he would get the dreaded avrdude error, ‘stk50… ...