I crossed the battery cables when jumping

It doesnt matter how dead the battery is reversing the jump can do damage.So have you taken the battery and had it tested yet and if its bad gotten a new one?Also do you have a multimeter to do some testing?

AAA took the old battery (car belongs to my step-******), Dealer charged her $4K for a new nav system and radio, etc. one of the really large 40A fuses was also blown. This was the third time the original battery went dead in less than 6 months. Could the reversed cables done that much damage? She was told that because of the "mistake" the warranty would not cover the expense..

Reversing a jump start can cause a lot of damge i dont blame the dealer for not covering damage from a reverse jump.So the battery was changed?Was the alternator tested and the electrical system tested for excessive draw?I would do that since the battery has gone dead several times before that.

Yep battery was changed, no one seems to know where the old one went. Car is running fine for now, but if the new battery loses charge, we'll know where to look. The way I see it is that the original problem is still there. Thanks for the info, very helpful but it doesn't make me feel very good about the screw up! (my bad for sure)

Your welcome thats what were here for.If you feel you still have a issue atleast go have the alternator tested they do that for free at the auto parts stores.Keep me posted.