如果单击Xcode 4.0.2中的“激活/取消激活断点”按钮，然后尝试添加断点，则不会生成断点。然后，如果我点击“断点导航器”Xcode崩溃。所以，显然有些事情是不对的。这是崩溃报告：
UNCAUGHT EXCEPTION (NSInvalidArgumentException): -[NSNull countByEnumeratingWithState:objects:count:]: unrecognized selector sent to instance 0x7fff701bbfa0
UserInfo: (null)
Hints:
0: Replacement view is installing: <IDEBreakpointNavigator: 0x201f19160 representing: <DVTExtension 0x20051eae0: Breakpoint Navigator (Xcode.IDEKit.Navigator.Breakpoints) v0.1>>
Backtrace:
0 0x00007fff80a57796 __exceptionPreprocess (in CoreFoundation)
1 0x00007fff822fd0f3 objc_exception_throw (in libobjc.A.dylib)
2 0x00007fff80ab1110 +[NSObject(NSObject) doesNotRecognizeSelector:] (in CoreFoundation)
3 0x00007fff80a2991f ___forwarding___ (in CoreFoundation)
4 0x00007fff80a25a68 _CF_forwarding_prep_0 (in CoreFoundation)
5 0x00000001175c2f13 -[IDEBreakpointNavigator _handleBreakpointsAdded:] (in DebuggerUI)
6 0x00007fff846a2f26 -[NSObject(NSKeyValueObserverRegistration) _addObserver:forProperty:options:context:] (in Foundation)
7 0x00007fff846a19cc -[NSObject(NSKeyValueObserverRegistration) addObserver:forKeyPath:options:context:] (in Foundation)
8 0x000000010001d9b5 -[DVTObservingBlockToken _setupObservingWithOptions:] (in DVTFoundation)
9 0x000000010001d8d3 -[DVTObservingBlockToken setHandlerBlock:forKeyPath:options:] (in DVTFoundation)
10 0x000000010001d6d8 -[NSObject(DVTObservingConvenience) dvt_newObserverForKeyPath:options:owner:withHandlerBlock:] (in DVTFoundation)
11 0x000000010001d662 -[NSObject(DVTObservingConvenience) dvt_newObserverForKeyPath:options:withHandlerBlock:] (in DVTFoundation)
12 0x00000001175c1a9d -[IDEBreakpointNavigator viewDidInstall] (in DebuggerUI)
13 0x00000001001d88a8 -[DVTControllerContentView _viewDidInstall] (in DVTKit)
14 0x00000001001d832a -[DVTControllerContentView viewDidMoveToWindow] (in DVTKit)
15 0x00007fff811f9b4f -[NSView _setWindow:] (in AppKit)
16 0x00007fff81202672 -[NSView addSubview:] (in AppKit)
17 0x00000001001de335 __42-[DVTReplacementView _setupViewController]_block_invoke_0 (in DVTKit)
18 0x0000000100031afd DVTInvokeWithFailureHint (in DVTFoundation)
19 0x00000001001de1d6 -[DVTReplacementView _setupViewController] (in DVTKit)
20 0x00000001001de0b8 -[DVTReplacementView installedViewController] (in DVTKit)
21 0x00000001001e8ff1 -[DVTReplacementView layoutTopDown] (in DVTKit)
22 0x00000001001d90e6 __84+[DVTAutoLayoutView _recursivelyLayoutSubviewsOfView:populatingSetWithLaidOutViews:]_block_invoke_0 (in DVTKit)
23 0x00000001001d918f __84+[DVTAutoLayoutView _recursivelyLayoutSubviewsOfView:populatingSetWithLaidOutViews:]_block_invoke_0 (in DVTKit)
24 0x00000001001d918f __84+[DVTAutoLayoutView _recursivelyLayoutSubviewsOfView:populatingSetWithLaidOutViews:]_block_invoke_0 (in DVTKit)
25 0x00000001001d918f __84+[DVTAutoLayoutView _recursivelyLayoutSubviewsOfView:populatingSetWithLaidOutViews:]_block_invoke_0 (in DVTKit)
26 0x00000001001d918f __84+[DVTAutoLayoutView _recursivelyLayoutSubviewsOfView:populatingSetWithLaidOutViews:]_block_invoke_0 (in DVTKit)
27 0x00000001001d918f __84+[DVTAutoLayoutView _recursivelyLayoutSubviewsOfView:populatingSetWithLaidOutViews:]_block_invoke_0 (in DVTKit)
28 0x00000001001d918f __84+[DVTAutoLayoutView _recursivelyLayoutSubviewsOfView:populatingSetWithLaidOutViews:]_block_invoke_0 (in DVTKit)
29 0x00000001001d8f33 +[DVTAutoLayoutView _recursivelyLayoutSubviewsOfView:populatingSetWithLaidOutViews:] (in DVTKit)
30 0x00000001001d8ce1 -[DVTAutoLayoutView viewWillDraw] (in DVTKit)
31 0x00007fff812d8e19 -[NSView viewWillDraw] (in AppKit)
32 0x00007fff812d8e19 -[NSView viewWillDraw] (in AppKit)
33 0x00007fff812d8e19 -[NSView viewWillDraw] (in AppKit)
34 0x00007fff812d8e19 -[NSView viewWillDraw] (in AppKit)
35 0x00007fff812d83ca -[NSView _sendViewWillDrawInRect:clipRootView:suppressRecursion:] (in AppKit)
36 0x00007fff81253b5d -[NSView displayIfNeeded] (in AppKit)
37 0x00007fff8124ea46 _handleWindowNeedsDisplay (in AppKit)
38 0x00007fff80a16b37 __CFRunLoopDoObservers (in CoreFoundation)
39 0x00007fff809f2464 __CFRunLoopRun (in CoreFoundation)
40 0x00007fff809f1dbf CFRunLoopRunSpecific (in CoreFoundation)
41 0x00007fff81c057ee RunCurrentEventLoopInMode (in HIToolbox)
42 0x00007fff81c05551 ReceiveNextEventCommon (in HIToolbox)
43 0x00007fff81c054ac BlockUntilNextEventMatchingListInMode (in HIToolbox)
44 0x00007fff81223e64 _DPSNextEvent (in AppKit)
45 0x00007fff812237a9 -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] (in AppKit)
46 0x00007fff811e948b -[NSApplication run] (in AppKit)
47 0x00007fff811e21a8 NSApplicationMain (in AppKit)
48 0x0000000100000eec
49 0x0000000000000002
其他人遇到过这个？
谢谢， 肖恩