Hi! i saw the same problem that i have in several forum topics, but in my case is in the mega adk arduino.
I have successfully upload projects before without a problem, but now i can't upload nothing.
I've tried using a lower version of the arduino software (from 1.0 to 0022) and nothing happened, even if i upload a simple code like the example blink.
What can i do? all the solutions i've read so far are for other arduino boards.
Can anybody help me pleaaaase! i need to make a presentation of my project in a few weeks! and my code is ready, all i need is to upload it!
Greetings from Chile! 
More information please. What operating system? What messages do you get?