Infamous Mega timeout

Using Arduino IDE 1.x
1

I've been using a Mega 2560 for months on an amateur radio project, with no problems uploading (mac running 10.6 and IDE 1.05). Today, I started getting the avrdude: stk500v2_ReceiveMessage(): timeout message. I've tried: restarting after deleting the preferences.txt file and disconnecting the USB cable. I have an Arduino board that accepts a sketch just fine, but when I unplug the Arduino and plug in the Mega, I get the above message.

I've really put in many hours on my project. Can someone explain how I might fix the Mega board? I've read the other topics on this, but none of those helped. Should I try reprogramming through the Arduino board? This is very discouraging.

2

I'm not sure if this will help, but might be a hint - I had the same problem with atmel studio in past - it was becouse atmel studio somehow changed default freq of comunciation with atmega - check you arvdude config if it's not too small.

3

Thanks for help. Punching reset button while uploading worked. Unhappily, button was buried between shields and deep in project case. In future, I'll always bring out a reset button by hard wire.