GameCenter Leaderboard in SpriteKit causing error

I finished my game in Sprite Kit and am now trying to store the highscore in GameCenter's Leaderboards. I followed some tutorials that worked great for none-spritekit-projects. Steps to my error:

1. I debug my app without any errors, some warnings but they do no harm.
2. App runs great, and my starting SKActions work flawless.
3. I log in to GameCenter succesfully.
4. When I touch the screen it freezes and gives me a "Missed Method" log error and "Thread 1:EXC_BAD_ACCESS (code=1, address=0x80000012)". Whenever I delete the line of code causing the BAD_ACESS error it pops up some other place in my code.

My Log:

2014-04-21 19:51:26.893 Sharky[3417:60b] Missed Method
2014-04-21 19:51:27.683 Sharky[3417:60b] -[NSMethodSignature copyWithZone:]: unrecognized selector sent to instance 0xacbdc20
2014-04-21 19:51:27.685 Sharky[3417:60b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSMethodSignature copyWithZone:]: unrecognized selector sent to instance 0xacbdc20'
*** First throw call stack:
(
    0   CoreFoundation                      0x0009c1e4 __exceptionPreprocess + 180
    1   libobjc.A.dylib                     0x019978e5 objc_exception_throw + 44
    2   CoreFoundation                      0x00139243 -[NSObject(NSObject) doesNotRecognizeSelector:] + 275
    3   CoreFoundation                      0x0008c50b ___forwarding___ + 1019
    4   CoreFoundation                      0x0008c0ee _CF_forwarding_prep_0 + 14
    5   libobjc.A.dylib                     0x019a9bcd -[NSObject copy] + 41
    6   SpriteKit                           0x01481f4c -[SKNode runAction:] + 55
    7   Sharky                              0x0000595c -[MyScene touchesBegan:withEvent:] + 476
    8   SpriteKit                           0x014702bf -[SKView touchesBegan:withEvent:] + 824
    9   UIKit                               0x00576c0b -[UIWindow _sendTouchesForEvent:] + 386
    10  UIKit                               0x005779d1 -[UIWindow sendEvent:] + 1117
    11  UIKit                               0x005495f2 -[UIApplication sendEvent:] + 242
    12  UIKit                               0x00533353 _UIApplicationHandleEventQueue + 11455
    13  CoreFoundation                      0x0002577f __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 15
    14  CoreFoundation                      0x0002510b __CFRunLoopDoSources0 + 235
    15  CoreFoundation                      0x000421ae __CFRunLoopRun + 910
    16  CoreFoundation                      0x000419d3 CFRunLoopRunSpecific + 467
    17  CoreFoundation                      0x000417eb CFRunLoopRunInMode + 123
    18  GraphicsServices                    0x03a7f5ee GSEventRunModal + 192
    19  GraphicsServices                    0x03a7f42b GSEventRun + 104
    20  UIKit                               0x00535f9b UIApplicationMain + 1225
    21  Sharky                              0x0000a472 main + 130
    22  libdyld.dylib                       0x023e4701 start + 1
    23  ???                                 0x00000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb)

Does anyone have any clue whats going on? Or does someone have a step-by-step tutorial on how to integrate GameCenter Leaderboards into a sprite kit project?