xcode error

ASSERTION FAILURE in /SourceCache/IDEInterfaceBuilderCocoaTouch/IDEInterfaceBuilderCocoaTouch-301/IBPlugin/Utilities/IBObjectMarshalling.m:136
Details:  Interface Builder encountered an error communicating with the iOS Simulator. "Interface Builder Cocoa Touch Tool" (5963) failed to launch and exited with status (null), signal 5. Please check Console.app for crash reports for "Interface Builder Cocoa Touch Tool" for further information.
Function: NSDistantObject<IBCocoaTouchToolProtocol> *IBAttachToCocoaTouchTool(IBCocoaTouchTargetRuntime *)
Thread:   <NSThread: 0x200020700>{name = (null), num = 1}
Hints:   None
Backtrace:
  0  0x000000010094c9c7 -[IDEAssertionHandler handleFailureInFunction:fileName:lineNumber:messageFormat:arguments:] (in IDEKit)
  1  0x0000000100060738 _DVTAssertionHandler (in DVTFoundation)
  2  0x0000000100070394 _DVTAssertionFailureHandler (in DVTFoundation)
  3  0x0000000117f35a48 IBAttachToCocoaTouchTool (in IDEInterfaceBuilderCocoaTouchIntegration)
  4  0x0000000117f355f0 IBAskClassInTargetRuntimeForValueForKeyPathUsingResultMarshallerWithContext (in IDEInterfaceBuilderCocoaTouchIntegration)
  5  0x0000000117f354a5 IBAskClassInTargetRuntimeForValueForKeyPathUsingResultMarshallerWithContext (in IDEInterfaceBuilderCocoaTouchIntegration)
  6  0x0000000117f34f8b IBUserPresentableStringForTargetedDeviceFamily (in IDEInterfaceBuilderCocoaTouchIntegration)
  7  0x0000000117f4cff0 IBIPhoneOSSdkToDeploymentTargetMapping (in IDEInterfaceBuilderCocoaTouchIntegration)
  8  0x0000000117f4d038 IBIPhoneOSSdkToDeploymentTargetMapping (in IDEInterfaceBuilderCocoaTouchIntegration)
  9  0x0000000117f51a02 IBUIControlEventTypeToUIControlEventMask (in IDEInterfaceBuilderCocoaTouchIntegration)
 10  0x00000001179a928b -[NSView(IBViewIntegration) ibWarnings:forDocument:withComputationContext:] (in IDEInterfaceBuilderKit)
 11  0x0000000117cdc8cf -[NSView(IBAppKitViewIntegration) ibSwizzledNSViewWarnings:forDocument:withComputationContext:] (in IDEInterfaceBuilderCocoaIntegration)
 12  0x0000000117f69589 IBUIViewSizeToFillView (in IDEInterfaceBuilderCocoaTouchIntegration)
 13  0x0000000117f709bd IBMakeBarButtonItemFromPasteboardView (in IDEInterfaceBuilderCocoaTouchIntegration)
 14  0x0000000117959d5e -[IBDocument rebuildWarnings] (in IDEInterfaceBuilderKit)
 15  0x0000000117959f85 -[IBDocument warnings] (in IDEInterfaceBuilderKit)
 16  0x0000000117a000ff -[IBIssueProvider updateWarningsForOpenDocument:filePath:] (in IDEInterfaceBuilderKit)
 17  0x0000000117945d0a -[IBIssueProvider updateOpenDocuments] (in IDEInterfaceBuilderKit)
 18  0x00007fff8158c08e NSKeyValueDidChange (in Foundation)
 19  0x00007fff8156f7c5 -[NSObject(NSKeyValueObserverNotification) didChangeValueForKey:] (in Foundation)
 20  0x000000010089d576 -[IDEDocumentController addDocument:] (in IDEKit)
 21  0x00000001008c4052 +[IDEDocumentController retainEditorDocument:] (in IDEKit)
 22  0x00000001008c3498 +[IDEDocumentController _retainedNewEditorDocumentWithClass:ofURL:ofType:extension:error:] (in IDEKit)
 23  0x00000001008c31bc -[IDEEditorContext _newEditorDocumentWithClass:ofURL:ofType:extension:] (in IDEKit)
 24  0x00000001008c2d05 -[IDEEditorContext _openNavigableItem:documentExtension:] (in IDEKit)
 25  0x000000010088e50f -[IDEEditorContext _openNavigableItem:] (in IDEKit)
 26  0x00000001008c2033 -[IDEEditorContext _notifyDelegateAndOpenNavigableItem:documentExtensionIdentifier:locationToSelect:annotationRepresentedObject:stateDictionary:annotationWantsIndicatorAnimation:exploreAnnotationRepresentedObject:] (in IDEKit)
 27  0x00000001008be678 -[IDEEditorContext _notifyDelegateAndOpenEditorOpenSpecifier:updateHistory:] (in IDEKit)
 28  0x00000001008be453 -[IDEEditorContext _openEditorOpenSpecifier:updateHistory:] (in IDEKit)
 29  0x00000001008be15e -[IDEEditorContext openEditorOpenSpecifier:] (in IDEKit)
 30  0x00000001008be13b -[IDEEditorModeViewController openEditorOpenSpecifier:editorContext:] (in IDEKit)
 31  0x00000001008be0f9 -[IDEEditorArea _openEditorOpenSpecifier:editorContext:takeFocus:] (in IDEKit)
 32  0x0000000100944bcb __108+[IDEEditorCoordinator _doOpenEditorOpenSpecifier:forWorkspaceTabController:editorContext:target:takeFocus:]_block_invoke_0 (in IDEKit)
 33  0x00000001008bde5d +[IDEEditorCoordinator _doOpenWithWorkspaceTabController:editorContext:target:allowFallback:documentURL:usingBlock:] (in IDEKit)
 34  0x0000000100944ae8 +[IDEEditorCoordinator _doOpenEditorOpenSpecifier:forWorkspaceTabController:editorContext:target:takeFocus:] (in IDEKit)
 35  0x00000001008bd899 -[_IDEOpenRequest _runIfNecessary] (in IDEKit)
 36  0x00007fff8159011c __NSFireDelayedPerform (in Foundation)
 37  0x00007fff84a8fbe8 __CFRunLoopRun (in CoreFoundation)
 38  0x00007fff84a8ddbf CFRunLoopRunSpecific (in CoreFoundation)
 39  0x00007fff828eb7ee RunCurrentEventLoopInMode (in HIToolbox)
 40  0x00007fff828eb5f3 ReceiveNextEventCommon (in HIToolbox)
 41  0x00007fff828eb4ac BlockUntilNextEventMatchingListInMode (in HIToolbox)
 42  0x00007fff85d1fe64 _DPSNextEvent (in AppKit)
 43  0x00007fff85d1f7a9 -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] (in AppKit)
 44  0x00007fff85ce548b -[NSApplication run] (in AppKit)
 45  0x00007fff85cde1a8 NSApplicationMain (in AppKit)
 46  0x0000000100000eec