Uno R3 Freezing up after prolonged inactivity?

I have a very simple set of code running on an UNO R3, it reads two potentiometer values, maps them to a number range, and then provides an average of the two numbers and outputs them to an LCD screen. The program works fine, everything goes as expected, however, if i leave the board running (this is on external power not via the USB, but it does the same either way) for more than a few hours with no input changes, the moment i make an input change to the potentiometer it basically crashes the board, the LCD clears and stops displaying data, when you reset the board it all works again as normal. It only crashes if i leave it for prolonged periods without input changes, does anyone have any ideas what may be causing this?