CEFO-

Rick has answered your questions very thoroughly (thanks Rick!) and I'll echo much of what he has said. I suspect the only reason you haven't received an invite yet is that other internal recs are "squeaking louder". Get your friends on the ball - they need to physically visit the recruiter(s) and find out if there is a problem with your application (NOT pushy, but very nicely - we don't want to alienate the one person who holds the key to your future.)

As far as your resignation, there really isn't enough information here to give a "best" answer. Rick has pointed out what the concerns might be - and I agree. If I was reviewing your application I would be asking, "why?" Does the job change make any logical sense? Are you committed to the profession? I would also pay attention to the other job changes you list. How often do you change employment? Watching carefully for any trends to explain your character.

Hope this helps!