I swear that there used to be a place to hide and show the exploded view sketch lines, but I can't find it in 2010. All I can think of now is to make sure that "Hide all types" is not checked in the drawing and that "Sketches" (and maybe "3D Sketches") is.
The above is all wrong. You have to go back in to the assembly file and show or hide the 3D Sketch that contains the sketch lines. As long as it is showing, it doesn't seem to matter whether you hide all types or don't show 3D sketches in the drawing.
Message was edited by: Jerry Steiger
Were the sketch lines drawn as construction lines? If not the only other thing I've come across is sometimes messing with the "show envelope" button in drawing view properties can make a difference.
I just came across the same thing. The view>show or hide sketches didn't seem to work, changing the sketch entities from construction to normal lines worked.