xCode 4 crashed

When i try open xib file from AppCode and xCode do not opened same project xCode was crash every time. When project was opened xCode some time.

Crash details from xCode

SSERTION FAILURE in /SourceCache/DVTFoundation/DVTFoundation-228/Framework/Classes/FoundationClassCategories/DVTNSKeyValueObserving.m:377
Details:  Assertion failed: [handlerBlocksByName objectForKey:name] == ((void*)0)
Object:   <DVTSharedObserver: 0x201128a60>
Method:   -setObserver:forName:handlerBlock:
Thread:   <NSThread: 0x200020e80>{name = (null), num = 1}
Hints:   None
Backtrace:
  0  0x0000000100949773 -[IDEAssertionHandler handleFailureInMethod:object:fileName:lineNumber:messageFormat:arguments:] (in IDEKit)
  1  0x000000010006d394 _DVTAssertionFailureHandler (in DVTFoundation)
  2  0x00000001000752e6 -[DVTSharedObserver setObserver:forName:handlerBlock:] (in DVTFoundation)
  3  0x0000000100075609 -[NSObject(DVTPropertyLinking) dvt_addObserverWithName:toKeyPath:ofObject:block:] (in DVTFoundation)
  4  0x0000000100a4d547 -[IDEDocumentController _showFileURLInEditorOfDocuments:] (in IDEKit)
  5  0x0000000100a4e05c -[IDEDocumentController _openSimpleFileURLs:documents:display:error:] (in IDEKit)
  6  0x000000010085bae4 -[IDEDocumentController _openDocumentsForURLs:display:error:] (in IDEKit)
  7  0x0000000100a4e094 -[IDEDocumentController openDocumentsWithContentsOfURLs:display:error:] (in IDEKit)
  8  0x00000001009436bb -[IDEApplicationController _openFiles:] (in IDEKit)
  9  0x00007fff87a41b52 -[NSApplication(NSAppleEventHandling) _handleAEOpenDocumentsForURLs:] (in AppKit)
10  0x00007fff8790e065 -[NSApplication(NSAppleEventHandling) _handleCoreEvent:withReplyEvent:] (in AppKit)
11  0x00007fff88a2e1c6 -[NSAppleEventManager dispatchRawAppleEvent:withRawReply:handlerRefCon:] (in Foundation)
12  0x00007fff88a2dff6 _NSAppleEventManagerGenericHandler (in Foundation)
13  0x00007fff865d632b aeDispatchAppleEvent(AEDesc const*, AEDesc*, unsigned int, unsigned char*) (in AE)
14  0x00007fff865d6224 dispatchEventAndSendReply(AEDesc const*, AEDesc*) (in AE)
15  0x00007fff865d612b aeProcessAppleEvent (in AE)
16  0x00007fff832ee619 AEProcessAppleEvent (in HIToolbox)
17  0x00007fff87813095 _DPSNextEvent (in AppKit)
18  0x00007fff87812801 -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] (in AppKit)
19  0x00007fff877d868f -[NSApplication run] (in AppKit)
20  0x00007fff877d13b0 NSApplicationMain (in AppKit)
21  0x0000000100000eec
22  0x0000000000000002