[Brian]

You may want to check and see if console.app has any additional information about what the error sound means. You'll find the app in your Utilities folder.

If you're having trouble getting your macs to see each other on Bonjor, you may want to check the firewall settings. Open System Preferences, select Security, and select the Firewall tab. You'll probably want to switch to "set access for specifc services and applications" and then use the Plus button to add OmniFocus to the list.

Once you've done that, set OmniFocus to "allow all incoming connections" - does that help?