Qtcreator integrated QtDesigner crashes on mac with qt5.1

Qtcreator integrated QtDesigner crashes on mac with qt5.1 when opening the ui file of the sample gui application.
This is a regression from 5.0.1
It does not affect the standalone designer.

Was after another bug, so I did not track down this but here is the stacktrace:

0 QWindow::handle 0x100755694
1 QCocoaNativeInterface::registerTouchWindow 0x102716430
2 QApplication::notify 0x10012a5cb
3 QCoreApplication::notifyInternal 0x100d75f42
4 QApplicationPrivate::dispatchEnterLeave 0x1001274ff
5 QApplicationPrivate::sendMouseEvent 0x100128a3d
6 QWidgetWindow::handleMouseEvent 0x10017a930
7 QWidgetWindow::event 0x100179d02
8 QApplicationPrivate::notify_helper 0x100127ccc
9 QApplication::notify 0x10012ab06
10 QCoreApplication::notifyInternal 0x100d75f42
11 QGuiApplicationPrivate::processMouseEvent 0x10074bc3b
12 QGuiApplicationPrivate::processWindowSystemEvent 0x10074b0a6
13 QWindowSystemInterface::sendWindowSystemEventsImplementation 0x10073e488
14 QWindowSystemInterface::sendWindowSystemEvents 0x10073e518
15 QCocoaEventDispatcherPrivate::processPostedEvents 0x102717b3e
16 QCocoaEventDispatcherPrivate::postedEventsSourceCallback 0x1027185ef
17 _CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION_ 0x7fff90d02b31
18 __CFRunLoopDoSources0 0x7fff90d02455
19 __CFRunLoopRun 0x7fff90d257f5
20 CFRunLoopRunSpecific 0x7fff90d250e2
... <More>