I can't seem to program the Arduino 2560 with the Ethernet shield attached. The shield works, it serves up a page fine, but when I goto program with it attached, the PC interface sits at "Uploading" indefinitely and doesn't display anything at all until I unplug power from the board. Anyone have a clue whats going on?
Two possibilities come immediately to mind. If you're using some form of Unix, there is a timing problem with the 8U2 chip and you will probably need to update it. You could have three exclamation points in a row somewhere in your code; that stops the bootloader and you will have to find them. Alternately, you could be suffering from a watchdog timer problem if you have one enabled. If a watchdog timer fails you have to power cycle the board before you can reload it. If everything works ok with the board removed, you may have a problem with the new reset circuitry on the ethernet board.