This exchange gave me the confidence to try restoring my 'bricked' atMEGA2560. Using Atmel Studio v6.1 programmer tool and a avrispmkII programmer, I located the file "stk500boot_v2_mega2560.hex" in my arduino/bootloaders directory. After feeding that to the programmer and writing it to the atMEGA2560 board, I fired up the Arduino application and sent the Blink application to the board ... I now have a happy, blinking LED!
My thanks to both of you for your previous efforts!
Now to try ONCE AGAIN to install Amforth on the atMEGA2560. Knowing that I can recover from a bad programming session, perhaps I'll prove successful, at some point, in getting the Amforth development system up and running! 