2009 Duramax, clicks, wont start

[09,3500]

Truck wouldn't start at store last week.

Replaced both batteries, still wouldn't start.

Smacked the starter and it started. So I replaced the starter Sunday night. Has worked GREAT for four days! Fired up beautifully a hour and half ago!

Now I'm stranded at the DMV cause I came back out and it won't crank. Just a click. Banged starter, still nothing but a click.

Five day old batteries and starter- where do I go from here other than crazy!?!?

[CamGTP]

Likely a connection problem. Bad cable or loose connection.