[CatOne]

Are you using MobileMe? Did you upgrade to the new MobileMe calendars?

Because OmniFocus needs a LOCAL calendar to sync to. That is, one that iCal says is "On my Mac." Create one of those in iCal and it will probably be available.

Unsure how this should work -- if OF will need to be upgraded to store stuff in CalDAV-based MobileMe calendars (probably)… this will change how things sync as server-based calendars no longer "sync" using MobileMe… they are on the server so no true sync is necessary.