See http://code.google.com/p/sumatrapdf/issues/detail?id=962 for a document which since http://darcs.ghostscript.com/darcsweb.cgi?r=mupdf;a=filediff;h=20100520214912-f546f-1d9a1cc35865aa9c69b5f43f18230aa77c7c4641.gz;f=fitz/dev_draw.c no longer renders as expected.
The scaled image dimensions were incorrectly calculated, so we ended up dividing by zero and getting the inverse matrix that maps from screen space to image space full of nans.