i just put a Messagebox behind the critical close(device) instruction
and achieved a nice crash with backtrace-log.
Maybe this could clear the situation:

int kparappWidget::pushButtonClose_clicked()
{
close(pardevice);
QMessageBox::about(this, tr("About Application"),
tr("The <b>Application</b> example demonstrates how to "
"write modern GUI applications using Qt, with a menu bar, "
"toolbars, and a status bar."));

return 0;
}

Backtrace log after crash:

System configuration startup check disabled.

Using host libthread_db library "/lib/libthread_db.so.1".
[Thread debugging using libthread_db enabled]
[New Thread 0xb6cf36d0 (LWP 21378)]
[KCrash handler]
#9 0xb6e21228 in main_arena () from /lib/libc.so.6
#10 0xb7461440 in QObject::QObject () from /usr/lib/qt3/lib/libqt-mt.so.3
#11 0xb749741d in QWidget::QWidget () from /usr/lib/qt3/lib/libqt-mt.so.3
#12 0xb75e7852 in QDialog::QDialog () from /usr/lib/qt3/lib/libqt-mt.so.3
#13 0xb7612c70 in QMessageBox::QMessageBox ()
from /usr/lib/qt3/lib/libqt-mt.so.3
#14 0xb7612d59 in QMessageBox::about () from /usr/lib/qt3/lib/libqt-mt.so.3
#15 0x0804ec16 in kparappWidget::pushButtonClose_clicked (this=0x80eb560)
at /home/op/sda-2/Programming/kdevelop-work/kparapp/src/kparappwidget.cpp:82
#16 0x0804f23a in kparappWidgetBase::qt_invoke (this=0x80eb560, _id=48,
_o=0xbfc780a8) at ./src/kparappwidgetbase.moc:104
#17 0x0804e999 in kparappWidget::qt_invoke (this=0x80eb560, _id=48,
_o=0xbfc780a8) at ./src/kparappwidget.moc:108
#18 0xb7460f1d in QObject::activate_signal ()
from /usr/lib/qt3/lib/libqt-mt.so.3
#19 0xb7461b5d in QObject::activate_signal ()
from /usr/lib/qt3/lib/libqt-mt.so.3
#20 0xb77a3b5c in QButton::clicked () from /usr/lib/qt3/lib/libqt-mt.so.3
#21 0xb74f4bfd in QButton::mouseReleaseEvent ()
from /usr/lib/qt3/lib/libqt-mt.so.3
#22 0xb7499880 in QWidget::event () from /usr/lib/qt3/lib/libqt-mt.so.3
#23 0xb74019c7 in QApplication::internalNotify ()
from /usr/lib/qt3/lib/libqt-mt.so.3
#24 0xb7402909 in QApplication::notify () from /usr/lib/qt3/lib/libqt-mt.so.3
#25 0xb7b7dd32 in KApplication::notify () from /opt/kde3/lib/libkdecore.so.4
#26 0xb73a0f57 in QETWidget::translateMouseEvent ()
from /usr/lib/qt3/lib/libqt-mt.so.3
#27 0xb73a00ff in QApplication::x11ProcessEvent ()
from /usr/lib/qt3/lib/libqt-mt.so.3
#28 0xb73b098a in QEventLoop::processEvents ()
from /usr/lib/qt3/lib/libqt-mt.so.3
#29 0xb74187f0 in QEventLoop::enterLoop () from /usr/lib/qt3/lib/libqt-mt.so.3
#30 0xb7418686 in QEventLoop::exec () from /usr/lib/qt3/lib/libqt-mt.so.3
#31 0xb740157f in QApplication::exec () from /usr/lib/qt3/lib/libqt-mt.so.3
#32 0x0804dec2 in main (argc=134547724, argv=0xb6e212e2)
at /home/op/sda-2/Programming/kdevelop-work/kparapp/src/main.cpp:69


cheers wally