prerender artifacts

Here I am again . . . knowing just enough to be dangerous. I'm doing a slide show with the basic Movie Studio. As a transition between slides, I'm using the push wipe. Because I added some quick moves and video brightness/contrast and black white effects to the stills, I prerender every so often so I can make sure my edits are to the music beats. BEFORE I prerender, my push wipe showed a small clean border that I had selected. AFTER prerendering, the border was gone and there's some funky dissolve or scan line looking thing in my 5 frame transition. Help?!?!?!