Hi oric_dan,
When I plug the Mega in, the red 'On' LED is lit, and the led connected to Pin13 is flashing (looks like it has the blink tutorial loaded).
When I attempt to upload, the tx/rx lights flash just once as the compiler tries to address the board, then just sits there giving timeout messages, with no further flashing of the tx/rx lights.
On my Uno and the Nano, the tx/rx lights flash furiously during upload as you describe.
Cheers,
Doug.