Final Draft is not a Apple product, not part of Final Cut Studio. You may want to contact Final Draft support.
If Final Draft won't open it's own documents, but other apps will open their documents, it's one of three things.
* Final Draft has a recent update bug (did you recently update your version?)
* Final Draft is corrupted and needs to be reinstalled
* The FDR document is corrupted
Since I'm not familiar with Final Draft, I don't know what to tell you outside of that. But I'm sure their tech support folks will be able to solve it very quickly for you.
You could, right off the bat, try deleting and reinstalling the application, which would take care of the majority of the trouble shooting problems.
