This often happens when switching branches with git etc.

Stacktrace:

Process: Qt Creator [13567]
Path: /Applications/Qt Creator 1.3 RC1.app/Contents/MacOS/Qt Creator
Identifier: com.nokia.qtcreator
Version: 1.2.94 (1.2.94)
Code Type: X86 (Native)
Parent Process: launchd [149]

Interval Since Last Report: 9626 sec
Crashes Since Last Report: 1
Per-App Interval Since Last Report: 52625 sec
Per-App Crashes Since Last Report: 1

Date/Time: 2009-11-18 10:26:03.669 +0100
OS Version: Mac OS X 10.5.8 (9L31a)
Report Version: 6
Anonymous UUID: 77DA3DA9-7658-4F00-B875-5D77CA559267

Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x00000000c7788934
Crashed Thread: 0

Thread 0 Crashed:
0 libQtCore.4.6.0.dylib 0x0040f49d QMetaObject::changeGuard(QObject*, QObject) + 295
1 libQtDesigner.4.6.0.dylib 0x10744ce4 qdesigner_internal::WidgetFactory::isPassiveInteractor(QWidget*) + 128
2 ...ignerComponents.4.6.0.dylib 0x10f165ed qdesigner_internal::WidgetEditorTool::handleEvent(QWidget*, QWidget*, QEvent*) + 51
3 ...ignerComponents.4.6.0.dylib 0x10eee49e qdesigner_internal::FormWindow::handleEvent(QWidget*, QWidget*, QEvent*) + 62
4 ...ignerComponents.4.6.0.dylib 0x10f04d75 qdesigner_internal::FormWindowManager::eventFilter(QObject*, QEvent*) + 949
5 libQtCore.4.6.0.dylib 0x003ffab4 QCoreApplicationPrivate::sendThroughApplicationEventFilters(QObject*, QEvent*) + 144
6 libQtGui.4.6.0.dylib 0x00d7f363 QApplicationPrivate::notify_helper(QObject*, QEvent*) + 33
7 libQtGui.4.6.0.dylib 0x00d866f2 QApplication::notify(QObject*, QEvent*) + 432
8 libQtCore.4.6.0.dylib 0x003ff807 QCoreApplication::notifyInternal(QObject*, QEvent*) + 99
9 libQtGui.4.6.0.dylib 0x00dce720 QWidget::setAttribute(Qt::WidgetAttribute, bool) + 1944
10 libQtGui.4.6.0.dylib 0x00dd621d QWidget::setAcceptDrops(bool) + 33
11 libQtGui.4.6.0.dylib 0x00d28e03 QWidget::destroy(bool, bool) + 463
12 libQtGui.4.6.0.dylib 0x00dcf538 QWidget::~QWidget() + 446
13 libQtCore.4.6.0.dylib 0x0040e085 QObjectPrivate::deleteChildren() + 119
14 libQtGui.4.6.0.dylib 0x00dcfcc6 QWidget::~QWidget() + 408
15 libQtGui.4.6.0.dylib 0x011c7d52 QPlainTextEdit::~QPlainTextEdit() + 74
16 libQtCore.4.6.0.dylib 0x0040e085 QObjectPrivate::deleteChildren() + 119
17 libQtGui.4.6.0.dylib 0x00dcfcc6 QWidget::~QWidget() + 408
18 libQtGui.4.6.0.dylib 0x0111dac9 QGroupBox::~QGroupBox() + 41
19 libQtCore.4.6.0.dylib 0x0040e085 QObjectPrivate::deleteChildren() + 119
20 libQtGui.4.6.0.dylib 0x00dcfcc6 QWidget::~QWidget() + 408
21 libQtDesigner.4.6.0.dylib 0x106fcdc1 QDesignerWidget::~QDesignerWidget() + 49
22 ...ignerComponents.4.6.0.dylib 0x10eee119 qdesigner_internal::FormWindow::clearMainContainer() + 125
23 ...ignerComponents.4.6.0.dylib 0x10eefc32 qdesigner_internal::FormWindow::setContents(QIODevice*) + 184
24 libDesigner.dylib 0x0f0b4447 Designer::FormWindowEditor::open(QString const&) + 321
25 libDesigner.dylib 0x0f0b338a Designer::FormWindowEditor::slotOpen(QString const&) + 24
26 libDesigner.dylib 0x0f0ca4b4 Designer::FormWindowEditor::qt_metacall(QMetaObject::Call, int, void**) + 190
27 libQtCore.4.6.0.dylib 0x0041220d QMetaObject::activate(QObject*, QMetaObject const*, int, void**) + 557
28 libDesigner.dylib 0x0f0ca5f5 Designer::Internal::FormWindowFile::reload(QString const&) + 61
29 libCore.dylib 0x01c181a7 Core::FileManager::checkForReload() + 927
30 libCore.dylib 0x01c8c7b6 Core::FileManager::qt_metacall(QMetaObject::Call, int, void**) + 212
31 libQtCore.4.6.0.dylib 0x0041220d QMetaObject::activate(QObject*, QMetaObject const*, int, void**) + 557
32 libQtCore.4.6.0.dylib 0x0041728b QSingleShotTimer::timeout() + 49
33 libQtCore.4.6.0.dylib 0x0041730e QSingleShotTimer::timerEvent(QTimerEvent*) + 44
34 libQtCore.4.6.0.dylib 0x0040ee47 QObject::event(QEvent*) + 553
35 libQtGui.4.6.0.dylib 0x00d7f3e5 QApplicationPrivate::notify_helper(QObject*, QEvent*) + 163
36 libQtGui.4.6.0.dylib 0x00d8676c QApplication::notify(QObject*, QEvent*) + 554
37 libQtCore.4.6.0.dylib 0x003ff807 QCoreApplication::notifyInternal(QObject*, QEvent*) + 99
38 libQtGui.4.6.0.dylib 0x00d7f7a8 qt_sendSpontaneousEvent(QObject*, QEvent*) + 54
39 libQtGui.4.6.0.dylib 0x00d35117 QEventDispatcherMacPrivate::activateTimer(__CFRunLoopTimer*, void*) + 147
40 com.apple.CoreFoundation 0x956e28f5 CFRunLoopRunSpecific + 4469
41 com.apple.CoreFoundation 0x956e2aa8 CFRunLoopRunInMode + 88
42 com.apple.HIToolbox 0x96e3a2ac RunCurrentEventLoopInMode + 283
43 com.apple.HIToolbox 0x96e3a0c5 ReceiveNextEventCommon + 374
44 com.apple.HIToolbox 0x96f7d377 ReceiveNextEvent + 58
45 libQtGui.4.6.0.dylib 0x00d355d1 QEventDispatcherMac::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) + 303
46 libQtCore.4.6.0.dylib 0x003fecab QEventLoop::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) + 63
47 libQtCore.4.6.0.dylib 0x003fef64 QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) + 172
48 libQtCore.4.6.0.dylib 0x00400806 QCoreApplication::exec() + 160
49 com.nokia.qtcreator 0x00008a5f main + 8967
50 com.nokia.qtcreator 0x00003cfe _start + 216
51 com.nokia.qtcreator 0x00003c25 start + 41