By default, the power-up states of the digital lines on E Series devices is a high-impedance input state. Below is a knowledge base that discusses how to pull these lines low initially using some pull down resistors. I hope this helps.
<a href="http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/b4fed0c879bd155f862569ed00142dc7?OpenDocument";>Setting the Default State of Digital Lines on E Series DAQ Boards</a>
