I'm using the latest beta available as of today. Now, OmniFocus will not quit (using File > Quit and command-q) and to quit you must force quit it -- this is the only way to make it quit. This is a new problem. Hope you please do fix it with the next beta release. (Haven't tried deleting prefs since I don't want to have to reconfigure everything, and not sure this would fix the problem anyway).
My system -- MacBook 2GHz, OS 10.4.11
My system -- MacBook 2GHz, OS 10.4.11