EXC_BAD_ACCES at object that exists (Does not appear on NSZombieEnabled)

Question

Hello everybody, I got an EXC_BAD_ACCES. I made upa n iPhone/iPad App, and one day testing it on iPhoneSimulator, I found that the app chrashes, when I´m trying to remove something from an array. I have a Selfmade object-class, called Box. In every box are 6 NSMutableArrays. In the init method, they are all alloced and inited, and of cause they have to be released in dealoc. And in this dealoc, I get an EXC_BAD_ACCES on the last array, although its handled exactly like the other five. I turned on NSZombieEnabled, to fight the bug. But it was away. Everything worked well. So I thought it might be just a bug of the iPhoneSimulator. Now I´m testing the App on a real device, and the Bug comes back. Not when I turn on NSZombieEnabled on Xcode and start it from there, but if I´m starting it on the device (an iPad 1) itself. So I tried different things: 1.) I set a breakpoint right before the release. I found out that the object is NOT released at this time. It has a place in the Memory, and it seems just like a complete object. This is strange, because such errors usually appear on overreleased objects. 2.) I tried to log the retainCount of the object. It ended in the same EXC_BAD_ACCES as the release. 3.) I tried to Log the retainCount of the object #5 wich is released before #6 without any kind of problem. This is intressting, because it leads to an bad_acces in the [array removeObjectAtIndex:... line. 4.) I thought: If there is an bad_acces on these objects, why should I release them? So I commented out the dealoc funktion. It worked. But instruments showed tons of leaks. So this is no option. In conclusion:
There is an EXC_BAD_ACCES although the objects are not overreleased.
This error does not appear with NSZombieEnabled
The objects are there, they EXIST, instruments shows that and Xcode, too. But there is an bad_acces anyway.
I am really confused, and I don´t know an answer, I have never seen anything like this before.
I´m waiting for iOS 5 with Garbage collector

Answer 1

EDIT:
I also tried
if (array) {
        [array release];
but it did crashed in the [array release]; line