I have the same issue with the Mega2560R3 board.
I have WinXP SP3 on a ThinkPad T-40. I have tried on a different machine with the same errors.
I tried the 'press the reset button' just after hitting the upload. Four tries and Blink finally uploaded.
Blink is running, but I wanted t play and changed the timing pause statements, but have not been able to upload.
I have tried the other ISP with no result.
My Com port shows Arduino Mega 2560 R3 (COM6) and the driver is usbser.sys Microsoft Corp 5.1.2600.5512(xpsp.080413-2108)
USB\VID_2341&PID_0042\64934333135351418100
I have selected the correct board and compost, and have used the AVRISP mkII
The RX light blinks once in a while.
Thoughts to help me get this running?
Ideas