When random number shows twice, my object crashes the iPhone app! :(

I'm working on a nice app as per usual and then this happens! You spin the wheel of fortune in my app, and when the spinning animation is finished, the app is supposed to randomize a number, and display the card matched as the number index.

The cards are stored in a NSMutableArray, working perfectly when called the first time. Eg. when the app randomizes number "1" card number 1 is called and displayed without problem! But once the randomizer hits "1" again, the app crashes on the line specified below.

Here's the code, PLEASE help me :)

NSNumber *cardNumber开发者_JS百科;
    cardNumber = [NSNumber numberWithUnsignedInt:arc4random()%[appDelegate.cardArray count]];

    NSLog(@"%@", cardNumber);

    SpinCard *selectedCard = [appDelegate.cardArray objectAtIndex:[cardNumber doubleValue]];

    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationDuration:0.5];
    [snurrKnapp setAlpha:100];
    [UIView setAnimationTransition:UIViewAnimationTransitionCurlDown forView:cardView cache:YES];
    [UIView commitAnimations];
    [snurrKnapp setEnabled:YES];
    if(![cardTitle.text isEqualToString:selectedCard.cardTitle]) { //Crashes here
        [cardTitle setText:selectedCard.cardTitle]; //If I remove the if-case it crashes here
        [cardContent setText:selectedCard.cardContent];
    }
    [selectedCard release];

Here's the error I get:

2011-04-21 23:10:54.296 Snurra Flaskan[947:707] 0
2011-04-21 23:10:58.794 Snurra Flaskan[947:707] 2
2011-04-21 23:11:02.691 Snurra Flaskan[947:707] 1
2011-04-21 23:11:08.977 Snurra Flaskan[947:707] 2
warning: Unable to read symbols for /Developer/Platforms/iPhoneOS.platform/DeviceSupport/4.3.1 (8G4)/Symbols/Developer/usr/lib/libXcodeDebuggerSupport.dylib (file not found).
(gdb) 

I'm very new in Obj-C, but here is what I think is happening.

You should not call [selectedCard release];

Because objectAtIndex does not allocate a new SpinCard for selectedCard. You should not release it. That explains the behaviour for the second use of that SpinCard: you can't use it, it has already been released.