Crash on second view transition - objective-c

Question

if (! self.mainPage)
{ self.mainPage= [[MainGameDisplay alloc] initWithNibName:nil bundle:nil]; }
[self presentViewController: self.mainPage animated:YES completion:NULL];
[self.view addSubview:self.mainPage.view];
self.mainPage.view.frame = CGRectMake(568, 0, 568, 320);//(N = horizontal, N = vertical)
[UIView animateWithDuration:1.0f
animations:^{
//actual frame needed with an animation.
self.mainPage.view.frame = CGRectMake(0, 0, 568, 320);
}
completion:^(BOOL finished) {
//ENTER HERE ANYTHING TO RUN AFTER ANIMATION IS COMPLETED:
[self presentViewController: self.mainPage animated:NO completion:NULL];
//This will make the next page load correctly after the transition, otherwise you cannot. interact with anything.
}];
#property (strong) MainGameDisplay *mainPage;
is declared in the .h file.
This code works perfectly but only once, If I was to transition to the mainPage view, come back and transition there again, it would crash at the end of the transition. I've played around so much to fix this but it just doesn't work.
=================
Stack Trace for MainGameDisplay viewDidLoad:
//First transition, A-Okay.
2012-11-11 12:27:07.547 Test_Game [584:c07] (
0 Test_Game 0x00002dab -[MainGameDisplay viewDidLoad] + 91
1 UIKit 0x000f8817 -[UIViewController loadViewIfRequired] + 536
2 UIKit 0x000f8882 -[UIViewController view] + 33
3 Test_Game 0x0000240e -[ViewController StartGame:] + 334
4 libobjc.A.dylib 0x010e3705 -[NSObject performSelector:withObject:withObject:] + 77
5 UIKit 0x0001a920 -[UIApplication sendAction:to:from:forEvent:] + 96
6 UIKit 0x0001a8b8 -[UIApplication sendAction:toTarget:fromSender:forEvent:] + 61
7 UIKit 0x000db671 -[UIControl sendAction:to:forEvent:] + 66
8 UIKit 0x000dbbcf -[UIControl(Internal) _sendActionsForEvents:withEvent:] + 578
9 UIKit 0x000dad38 -[UIControl touchesEnded:withEvent:] + 546
10 UIKit 0x0004a33f -[UIWindow _sendTouchesForEvent:] + 846
11 UIKit 0x0004a552 -[UIWindow sendEvent:] + 273
12 UIKit 0x000283aa -[UIApplication sendEvent:] + 436
13 UIKit 0x00019cf8 _UIApplicationHandleEvent + 9874
14 GraphicsServices 0x01beddf9 _PurpleEventCallback + 339
15 GraphicsServices 0x01bedad0 PurpleEventCallback + 46
16 CoreFoundation 0x01c07bf5 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 53
17 CoreFoundation 0x01c07962 __CFRunLoopDoSource1 + 146
18 CoreFoundation 0x01c38bb6 __CFRunLoopRun + 2118
19 CoreFoundation 0x01c37f44 CFRunLoopRunSpecific + 276
20 CoreFoundation 0x01c37e1b CFRunLoopRunInMode + 123
21 GraphicsServices 0x01bec7e3 GSEventRunModal + 88
22 GraphicsServices 0x01bec668 GSEventRun + 104
23 UIKit 0x0001765c UIApplicationMain + 1211
24 Test_Game 0x00001cfd main + 141
25 Test_Game 0x00001c25 start + 53
)
//Second transition, crashes now.
2012-11-11 12:27:11.223 Test_Game [584:c07] (
0 Test_Game 0x00002dab -[MainGameDisplay viewDidLoad] + 91
1 UIKit 0x000f8817 -[UIViewController loadViewIfRequired] + 536
2 UIKit 0x000f8882 -[UIViewController view] + 33
3 Test_Game 0x0000240e -[ViewController StartGame:] + 334
4 libobjc.A.dylib 0x010e3705 -[NSObject performSelector:withObject:withObject:] + 77
5 UIKit 0x0001a920 -[UIApplication sendAction:to:from:forEvent:] + 96
6 UIKit 0x0001a8b8 -[UIApplication sendAction:toTarget:fromSender:forEvent:] + 61
7 UIKit 0x000db671 -[UIControl sendAction:to:forEvent:] + 66
8 UIKit 0x000dbbcf -[UIControl(Internal) _sendActionsForEvents:withEvent:] + 578
9 UIKit 0x000dad38 -[UIControl touchesEnded:withEvent:] + 546
10 UIKit 0x0004a33f -[UIWindow _sendTouchesForEvent:] + 846
11 UIKit 0x0004a552 -[UIWindow sendEvent:] + 273
12 UIKit 0x000283aa -[UIApplication sendEvent:] + 436
13 UIKit 0x00019cf8 _UIApplicationHandleEvent + 9874
14 GraphicsServices 0x01beddf9 _PurpleEventCallback + 339
15 GraphicsServices 0x01bedad0 PurpleEventCallback + 46
16 CoreFoundation 0x01c07bf5 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 53
17 CoreFoundation 0x01c07962 __CFRunLoopDoSource1 + 146
18 CoreFoundation 0x01c38bb6 __CFRunLoopRun + 2118
19 CoreFoundation 0x01c37f44 CFRunLoopRunSpecific + 276
20 CoreFoundation 0x01c37e1b CFRunLoopRunInMode + 123
21 GraphicsServices 0x01bec7e3 GSEventRunModal + 88
22 GraphicsServices 0x01bec668 GSEventRun + 104
23 UIKit 0x0001765c UIApplicationMain + 1211
24 Test_Game 0x00001cfd main + 141
25 Test_Game 0x00001c25 start + 53
)

Answer 1

maybe you release you property in viewDidDisapear or something like this ?
what type of crash - BAD_ACCESS ?