Actually, I removed the textures from the model before I rendered. The dark streaks are just what Poser does with really long, skinny triangles. (And I know I didn't miss any, because I had to go through each material one by one, since they have uninformative names like 1, 2, 3...)

It's a pretty good model aside from that, and the crooked text on the port side. It looks like what's it supposed to look like (a custom shuttle from Star Trek, weird window frame and all).