Inactive Recognized Developer
Oh FFS dude... there are *multiple* threads already discussing this, use search (if you can't be bothered to read the full thread for a given hack before trying to apply it, which you should be doing anyhow). There's bold text RIGHT AT THE TOP OF THE INTEROP UNLOCK THREAD telling you that it wouldn't work...
If you didn't install Diagnosis before installing the Samsung update that comes with GDR3 (it's not GDR3 itself that's the problem, it's the Samsung firmware update), then you will need to roll back to an older ROM. Simple as that. I'd like to find a new approach, but I'm mostly focusing on getting root on Samsung phones, and on non-Samsung-specific interop hacks, for now.