Arduino is playing favorites!

I am having a weird problem uploading (via USB) using Arduino .23 to a "2560" series board. I should mention that I have two "2560" boards and Arduino works with one of them correctly. Both com ports have been set up exactly the same...Com Port speed is 115,200, "set RTS on close" is checked for both. The FTDI driver is the same being used for both boards.

The first board works correctly, Arduino compiles and the sketch size is displayed, a moment later the red and green "flight mode" lights disappear and the receive and transmit lights crank until the code is uploaded. After the code is uploaded there is a slight delay and the board reboots and goes back to flashing red and green. All is good.
On the second board: Arduino compiles and the sketch size is displayed and the announcement is made that it is uploading...Arduino then sticks in that mode displaying no errors at all and never completes the upload. BUT, what happens on the APM board side is that after the sketch size is displayed the red and green light go out momentarily while the amber receive light blinks for about 2 seconds... the transmit light does not handshake blink with the receive light. After this 2 second time period the red and green light start to blink again as if nothing ever happened. 
Has anyone seen this before? I have searched exhaustively for an answer but the fact that this works for one board and not the other has me puzzled. Thanks for any input...

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  • i've seen some other threads on diyd with some problems but haven't seen a solution yet. it might be the same problem or might not :)

    Some questions

    has the board with the problem ever worked?

    which usb driver do you have installed?

    have your tried resetting usb by powering your computer down?

    what happens if you press the reset on the board about the same time (or just after) that arduino reports the program size?

    do you have a programmer?

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