[DerekM]

This is a bug in OmniGraffle's exporter to OO3 format. Font weights are being stored incorrectly and can end up as negative values when it should be between 1 and 14. OmniOutliner apparently can't handle this and you'll end up in a horrible state making you force quit. We'll try to get this fixed on both ends. Before exporting to OO3 format, you'll need to change the font weight on all the text to regular (the Typeface option in the font panel). Sorry for the trouble!