Version:           unspecified (using Devel) 
OS:                Linux

When I play a classical (9x9) sudoku, I see in the stdout:

ksudoku(23883): Failed to lock file "" , last result = 2 
ksudoku(23883)/kdeui (KIconLoader): Unable to lock pixmap cache when trying to discard it 
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::end: Painter not active, aborted
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::end: Painter not active, aborted
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::end: Painter not active, aborted
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::end: Painter not active, aborted
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::end: Painter not active, aborted
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::end: Painter not active, aborted
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::end: Painter not active, aborted
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::end: Painter not active, aborted
QPainter::begin: Paint device returned engine == 0, type: 2
QPainter::end: Painter not active, aborted
Couldn't find node block_1234. Skipping rendering.
Couldn't find node block_1234. Skipping rendering.
Couldn't find node block_1234. Skipping rendering.


Reproducible: Always

Steps to Reproduce:
setting the environment variable QT_FATAL_WARNINGS=1 you can see exactly where it happens.
For example:
#12 0x00007fc0df11f310 in QPainter::QPainter (this=0x7fff83faf930, pd=0x7fff83faf8c0) at /g/kde4svn/qt/src/gui/painting/qpainter.cpp:1491
#13 0x0000000000429300 in ksudoku::Renderer::renderSpecial (this=0x659f80, type=<value optimized out>, size=-1) at /g/kde4svn/kdegames/ksudoku/src/gui/views/renderer.cpp:167
#14 0x000000000042b2bc in ksudoku::SymbolItem::setSize (this=0x144ea80, size=-1) at /g/kde4svn/kdegames/ksudoku/src/gui/views/valuelistwidget.cpp:62
#15 0x000000000042b7dc in ksudoku::ValueListWidget::resizeEvent (this=0xe5f960) at /g/kde4svn/kdegames/ksudoku/src/gui/views/valuelistwidget.cpp:165
#16 0x000000000042b96d in ksudoku::ValueListWidget::setMaxValue (this=0xe5f960, maxValue=9) at /g/kde4svn/kdegames/ksudoku/src/gui/views/valuelistwidget.cpp:156
#17 0x000000000041793a in KSudoku::startGame (this=0xd24000, game=<value optimized out>) at /g/kde4svn/kdegames/ksudoku/src/gui/ksudoku.cpp:241