you could run a conflict test with Conflict Catcher. I found this works noticeably better than trial or error.
Ash, I've always had excellent luck with Apple Support. I just make sure to treat them like human beings, explain the problem, explain what I've done already and be prepared to sit by your machine and try stuff when they tell you to.
I've been using Macs since '95 and don't have a single support horror story to tell, for what that's worth.