So as a beginner, a newbie to kitesurfing, and a newbie to Seabreeze your willing to go out on a limb and pay out on one of the few Australian brands that we have.
That's some pretty poor form!
If you had bought it new then i'd say you have every right to complain... but you didn't.
Did you go into your local kite shop and ask them for assistance? If you did you would have found that having them replace the clam cleat also would have fixed it and cost you under $20.
Did you ask anyone else more experience than you to take a look at it? If you did then they could also confirm if it was a worn clam cleat or depower rope.
Did you take one ounce of initiative in resolving this matter? Umm... well you did post on Seabreeze, so 2 points.

[}:)]
I'm going to defend Chris from Griffin here and say that everything that i've heard of Griffin Kiteboarding and all of my experiences with their kites have been superb.
I fear for who ever you bought the Cabrinha from!