Arduino, Ramps 1.4 and Marlin 1.1 [SOLVED]

This is a strange one, I have built my own printer using a mega 2560 and Ramps 1.4 which behaves as expected when using menus providing the USB is not connected. When the USB is plugged in, any attempt to extrude results in the extruder motor running non stop from both the LCD menu or gcodes. The serial monitor shows messages that Marlin is busy. This happens with the USB plugged in but no active connection to the printer. My suspicion is some kind of power issue but not sure where to start. Has anybody encountered this problem before?

*EDIT*

It turns out enabling the eeprom settings was the cause, so a software issue. Very strange manifestation though

Edited 1 time(s). Last edit at 05/13/2017 07:46AM by Aethelstan.