title: How to solve KERN_PROTECTION_FAILURE and KERN_INVALID_ADDRESS?
body: <p>How can you solve a KERN_PROTECTION_FAILURE and a KERN_INVALID ADDRESS?
  Both seem to happen at exactly the same spot when I run my app.</p>
  
  <pre><code>Exception Type:  EXC_BAD_ACCESS (SIGSEGV)
  Exception Codes: KERN_INVALID_ADDRESS at 0x6d783f44
  Crashed Thread:  2
  
  Thread 2 Crashed:
  0   libobjc.A.dylib                 0x34a80464 objc_msgSend + 16
  1   Foundation                      0x31171dda __+[__NSOperationInternal _observeValueForKeyPath:ofObject:changeKind:oldValue:newValue:indexes:context:]_block_invoke_7 + 10
  2   libSystem.B.dylib               0x30dd9678 _dispatch_call_block_and_release + 12
  3   libSystem.B.dylib               0x30dd9b98 _dispatch_worker_thread2 + 120
  4   libSystem.B.dylib               0x30d7e24a _pthread_wqthread + 258
  5   libSystem.B.dylib               0x30d76970 start_wqthread + 0
  </code></pre>
  
  <p>And:</p>
  
  <pre><code>Exception Type:  EXC_BAD_ACCESS (SIGBUS)
  Exception Codes: KERN_PROTECTION_FAILURE at 0x00000011
  Crashed Thread:  7
  
  Thread 7 Crashed:
  0   libobjc.A.dylib                 0x34a80464 objc_msgSend + 16
  1   Foundation                      0x31171dfc -[NSOperation completionBlock] + 16
  2   Foundation                      0x31171dda __+[__NSOperationInternal _observeValueForKeyPath:ofObject:changeKind:oldValue:newValue:indexes:context:]_block_invoke_7 + 10
  3   libSystem.B.dylib               0x30dd9678 _dispatch_call_block_and_release + 12
  4   libSystem.B.dylib               0x30dd9b98 _dispatch_worker_thread2 + 120
  5   libSystem.B.dylib               0x30d7e24a _pthread_wqthread + 258
  6   libSystem.B.dylib               0x30d76970 start_wqthread + 0
  </code></pre>
  
  <p>Weird thing is, it crashes on an iPad 1 (iOS 4.2.1) but not on an iPad 2 (iOS 4.3.2).
  Could this maybe be a problem with the iPad itself or maybe with the memory? Or is it truly a bug in my code? If so, why can't I reproduce it on the iPad 2?</p>