I have a little sketch that works perfectly on a Pro Mini and a 4D Systems touch LCD. I can touch a button and it shoots down the serial port a 7 group of numbers. Now I have taken this sketch and migrated it to the Mega 2560. And changed all of the software serial calls to Serial1, Serial2, and Serial3. I have made sure that the display that was just serial is now on Serial1 with wires from the connector to Pins 18 and 19 (RX1 & TX1) on the board. And so forth for the other two connectors (bar code scanner and printer) for Serial2 & 3. I have even swapped my RX & TX lines for the display to see if I got them turned around. Nothing. Display resets when I upload a sketch and when I open the serial com port to see what is coming out of the Serial port (the USB interface).
Any ideas what the difference might be between the Pro Mini and Mega 2560 that I might have missed?