Sorry for the trouble here, Aestus - this error message sounds familiar, but I don't know what steps our support ninjas use to help folks that hit it. If you email
omnigraffle@omnigroup.com, they can help.
(We collectively spend as much time as we can on the forums after our other responsibilities are squared away, but we can't guarantee that a person from a specific team will see a post in a given timeframe. If you need the most rapid response, email or phone (800.315.6664) is the way to go.)