OS X: switching window from maximized to normal crashes our program

we implemented a button in our program to switch between normal window and fullscreen mode. this feature crashes on mac os. (both 10.8 and 10.9)

we don't recall seeing this with Qt4.

call stack:

Version: ???
Code Type: X86-64 (Native)
Parent Process: launchd [255]
User ID: 501

Date/Time: 2014-08-29 16:21:48.485 -0700
OS Version: Mac OS X 10.8.5 (12F45)
Report Version: 10

Interval Since Last Report: 891 sec
Crashes Since Last Report: 2
Per-App Crashes Since Last Report: 2
Anonymous UUID: E0003C9C-4BE3-D9F6-7416-C6C36EF971EA

Crashed Thread: 0 Dispatch queue: com.apple.main-thread

Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x0000000000000000

VM Regions Near 0:
-->
__TEXT 0000000100000000-0000000100687000 [ 6684K] r-x/rwx SM=COW /Users/USER/Desktop/GRID Workspace.app/Contents/MacOS/GRID Workspace.app/Contents/MacOS/GRID Workspace

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0 QtGui 0x0000000101814229 QPaintEngine::syncState() + 9
1 QtWidgets 0x000000010107870d 0x10106f000 + 38669
2 QtWidgets 0x0000000101080264 0x10106f000 + 70244
3 QtWidgets 0x0000000101136400 0x10106f000 + 816128
4 QtWidgets 0x00000001011b46bc QFrame::drawFrame(QPainter*) + 284
5 QtWidgets 0x00000001011b9eae QLabel::paintEvent(QPaintEvent*) + 62
6 QtWidgets 0x00000001010d46c6 QWidget::event(QEvent*) + 1958
7 QtWidgets 0x00000001011b4867 QFrame::event(QEvent*) + 183
8 QtWidgets 0x00000001011b9e47 QLabel::event(QEvent*) + 247
9 QtWidgets 0x000000010109c2dc QApplicationPrivate::notify_helper(QObject*, QEvent*) + 300
10 QtWidgets 0x000000010109ed9b QApplication::notify(QObject*, QEvent*) + 6187
11 QtCore 0x0000000101d4aa52 QCoreApplication::notifyInternal(QObject*, QEvent*) + 114
12 QtWidgets 0x00000001010cf325 QWidgetPrivate::drawWidget(QPaintDevice*, QRegion const&, QPoint const&, int, QPainter*, QWidgetBackingStore*) + 2997
13 QtWidgets 0x00000001010cfa7a QWidgetPrivate::paintSiblingsRecursive(QPaintDevice*, QList<QObject*> const&, int, QRegion const&, QPoint const&, int, QPainter*, QWidgetBackingStore*) + 1146
14 QtWidgets 0x00000001010cf5c6 QWidgetPrivate::drawWidget(QPaintDevice*, QRegion const&, QPoint const&, int, QPainter*, QWidgetBackingStore*) + 3670
15 QtWidgets 0x00000001010cfa7a QWidgetPrivate::paintSiblingsRecursive(QPaintDevice*, QList<QObject*> const&, int, QRegion const&, QPoint const&, int, QPainter*, QWidgetBackingStore*) + 1146
16 QtWidgets 0x00000001010cf5c6 QWidgetPrivate::drawWidget(QPaintDevice*, QRegion const&, QPoint const&, int, QPainter*, QWidgetBackingStore*) + 3670
17 QtWidgets 0x00000001010cfa7a QWidgetPrivate::paintSiblingsRecursive(QPaintDevice*, QList<QObject*> const&, int, QRegion const&, QPoint const&, int, QPainter*, QWidgetBackingStore*) + 1146
18 QtWidgets 0x00000001010cf5c6 QWidgetPrivate::drawWidget(QPaintDevice*, QRegion const&, QPoint const&, int, QPainter*, QWidgetBackingStore*) + 3670
19 QtWidgets 0x00000001010cfa7a QWidgetPrivate::paintSiblingsRecursive(QPaintDevice*, QList<QObject*> const&, int, QRegion const&, QPoint const&, int, QPainter*, QWidgetBackingStore*) + 1146
20 QtWidgets 0x00000001010cf5c6 QWidgetPrivate::drawWidget(QPaintDevice*, QRegion const&, QPoint const&, int, QPainter*, QWidgetBackingStore*) + 3670
21 QtWidgets 0x00000001010a74c8 0x10106f000 + 230600
22 QtWidgets 0x00000001010a77ee 0x10106f000 + 231406
23 QtWidgets 0x00000001010c6a03 QWidgetPrivate::syncBackingStore() + 211
24 QtWidgets 0x00000001010d496d QWidget::event(QEvent*) + 2637
25 QtWidgets 0x00000001011ca7e7 QMainWindow::event(QEvent*) + 935
26 QtWidgets 0x000000010109c2dc QApplicationPrivate::notify_helper(QObject*, QEvent*) + 300
27 QtWidgets 0x000000010109ed9b QApplication::notify(QObject*, QEvent*) + 6187
28 QtCore 0x0000000101d4b5d7 QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) + 631
29 libqcocoa.dylib 0x00000001036a2ced 0x103683000 + 130285
30 libqcocoa.dylib 0x00000001036a3571 0x103683000 + 132465
31 com.apple.CoreFoundation 0x00007fff88086b31 _CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION_ + 17
32 com.apple.CoreFoundation 0x00007fff8808651d __CFRunLoopDoSources0 + 445
33 com.apple.CoreFoundation 0x00007fff880a97f5 __CFRunLoopRun + 789
34 com.apple.CoreFoundation 0x00007fff880a90e2 CFRunLoopRunSpecific + 290
35 com.apple.HIToolbox 0x00007fff8a66eeb4 RunCurrentEventLoopInMode + 209
36 com.apple.HIToolbox 0x00007fff8a66eb94 ReceiveNextEventCommon + 166
37 com.apple.HIToolbox 0x00007fff8a66eae3 BlockUntilNextEventMatchingListInMode + 62
38 com.apple.AppKit 0x00007fff8eb5c533 _DPSNextEvent + 685
39 com.apple.AppKit 0x00007fff8eb5bdf2 -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] + 128
40 com.apple.AppKit 0x00007fff8eb531a3 -[NSApplication run] + 517
41 libqcocoa.dylib 0x00000001036a2425 0x103683000 + 128037
42 QtCore 0x0000000101d47acd QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) + 381
43 QtCore 0x0000000101d4b007 QCoreApplication::exec() + 359
44 com.nvidia.GRID Workspace 0x000000010000a4cb main + 7275
45 com.nvidia.GRID Workspace 0x0000000100007ab4 start + 52