There is also the possibility of the the controller itself being placed the wrong way in the socket on the Arduino. This can be dangerous for the controller (which may get zapped) but, in my case, it only gave the out of sync error, preventing me from uploading code.

So just check if the notch on the IC is in the right direction (you can cross check with images of board online). The notch on the Uno's controller should point towards edge of board.