[Lizard]

Is OmniFocus already running? If it's not running, and you have old versions of OmniFocus on the machine (pretty likely if you started using it back during the betas), it's possible the system is picking the wrong version of Focus to send the data to and it's getting messed up. (I just tried it and that's what happened for me.) You may need to delete those older versions of OmniFocus.app to get the OS to stop being stupid.

If OmniFocus is already running when you try to use the service, I'm not sure what's going on -- your best bet is probably to email our support ninjas (omnifocus@omnigroup.com).