Shiner:
I know how bad programmers can get - I talk to them all day, every day.
It is NEVER thier fault, even when you correct thier code and it all works.
In this scenario, here is a typical start:
Me: "How long has it been doing this?"
Them:
A) "Oh, about (amount of time) now."
B) "Its always done this"
IF A:
Me: "What changed?"
Them: "Nothing!"
Me: "Nothing at all?"
Them: "Not one tiny thing! Except that we applied a patch to the client/app/DB"
Me: "Ah ha!"
Concentrate on what changed from there.
IF B:
Me:"What happened in testing? We need to go back and look at the architecture and performance of this app in test scenarios."
Them: "It was fine in test!"
Me: "OK, so whats different between test and dev?"
Them: "Nothing!"
Me: "Nothing?"
Them: "Nothing at all except that the DB is version 7.1 in test and its 8.2 in dev..."
etc.
Them: "Nothing!