Sorry for the trouble, CPG - it'll probably be easiest for us to help if you send email to
omnigraffle@omnigroup.com or give us a call at 800.315.6664.
(Since the printer drivers that are being used are have a pretty strong effect on issues like this, it's often difficult to troubleshoot something like this via forum post; we generally need to get screenshots of Page Setup and the print panel, or ask you to read stuff off to us if we're on the phone.)