[Brian]

There are a couple different things that could be going on here - can you give us more information about your setup? In the screenshot you included, is that a PDF file that's been exported back from the Windows machine, a chunk of the screen from Parallels/VMWare, something else?

This could be due to different display settings in the two OSes, a problem in OmniGraffle, or something else entirely. Need more info. :-)