Error when trying to print a Packing slip

I'm getting this error when I try to print a packing slip. Any ideas?

Unexpected error processing messages msg=2234, hwnd=263176 wParam=0, IPram=170115744, Unable to call My.ShipRush. 151:500 Internal Server Error. Unable to POST to "https://api.my.shiprush.com/packinglistservice/packinglist/get" (windows)



Windows 7 64bit