Did you re-flash the stock firmware? If so, then it's most likely not the programming or firmware.
The RAMBo is a circuit board, and components on circuit boards can go bad. If that happened to components that directly affect the LCD pins, then you'd have trouble.
You could try replacing the RAMBo board to logically determine if that's the problem. If you do and you still have the same problem, you know the problem is elsewhere. But given the other troubleshooting steps you've tried, that is possible.