What does it mean if Im seeing an “Unable to lock Document. Another application has the OmniFocus document locked” error?
Try logging out and back in, or if that does not work, rebooting. This will clear up any issues if a second copy of OmniFocus is somehow running, causing a conflict with the lock on the database. If that does not help and you are sure that there is not another instance of OmniFocus that is currently running and thus legitimately has the database locked, locate your OmniFocus database in ~/Library/Application Support/OmniFocus and look for a file there with a “.lock” filename extension. Delete this file and relaunch OmniFocus.