... I'm trying to decide whether I should stop spoon-feeding you answers or just go on and hope eventually you'll run out of them.
There are a bunch of forum threads about GDR3 and interop-unlock. Short version: installing the Samsung update that comes with retail GDR3 will prevent interop-unlock. There are ways around it, which you should read up on as well because, while it doesn't re-lock your phone, it *does* make interop-unlock much less useful too.