There is an occasional segmentation fault on application start with the following back trace:

(gdb) bt
#0 0xb6bb33ea in QSortFilterProxyModel::parent(QModelIndex const&) const ()
from /usr/lib/libQtGui.so.4
#1 0xb715c0c0 in ?? () from /usr/lib/python2.7/site-packages/PyQt4/QtGui.so
#2 0xb6b653a6 in QTreeView::indexRowSizeHint(QModelIndex const&) const ()
from /usr/lib/libQtGui.so.4
#3 0xb6b694f3 in QTreeViewPrivate::itemHeight(int) const ()
from /usr/lib/libQtGui.so.4
#4 0xb6b697cb in QTreeViewPrivate::updateScrollBars() ()
from /usr/lib/libQtGui.so.4
#5 0xb6b69af8 in QTreeView::updateGeometries() () from /usr/lib/libQtGui.so.4
#6 0xb70835f0 in ?? () from /usr/lib/python2.7/site-packages/PyQt4/QtGui.so
#7 0xb6b1b086 in QAbstractItemView::resizeEvent(QResizeEvent*) ()
from /usr/lib/libQtGui.so.4
#8 0xb708aa14 in ?? () from /usr/lib/python2.7/site-packages/PyQt4/QtGui.so
#9 0xb65ca9df in QWidget::event(QEvent*) () from /usr/lib/libQtGui.so.4
#10 0xb69e6496 in QFrame::event(QEvent*) () from /usr/lib/libQtGui.so.4
#11 0xb6a7a072 in QAbstractScrollArea::viewportEvent(QEvent*) ()
from /usr/lib/libQtGui.so.4
#12 0xb6b1f34c in QAbstractItemView::viewportEvent(QEvent*) ()
from /usr/lib/libQtGui.so.4
#13 0xb6b6dc47 in QTreeView::viewportEvent(QEvent*) ()
from /usr/lib/libQtGui.so.4
#14 0xb708c4cc in ?? () from /usr/lib/python2.7/site-packages/PyQt4/QtGui.so
#15 0xb6a7c836 in ?? () from /usr/lib/libQtGui.so.4
#16 0xb7873af6 in QCoreApplicationPrivate::sendThroughObjectEventFilters(QObject*, QEvent*) () from /usr/lib/libQtCore.so.4
#17 0xb656fc73 in QApplicationPrivate::notify_helper(QObject*, QEvent*) ()
from /usr/lib/libQtGui.so.4
#18 0xb657511b in QApplication::notify(QObject*, QEvent*) ()
from /usr/lib/libQtGui.so.4
#19 0xb73c7270 in ?? () from /usr/lib/python2.7/site-packages/PyQt4/QtGui.so
#20 0xb787394e in QCoreApplication::notifyInternal(QObject*, QEvent*) ()
from /usr/lib/libQtCore.so.4
#21 0xb65c4e2b in QWidgetPrivate::sendPendingMoveAndResizeEvents(bool, bool) ()
from /usr/lib/libQtGui.so.4
#22 0xb65cd9f9 in QWidgetPrivate::show_helper() () from /usr/lib/libQtGui.so.4
#23 0xb65cde61 in QWidget::setVisible(bool) () from /usr/lib/libQtGui.so.4
#24 0xb65cd978 in QWidgetPrivate::showChildren(bool) ()
from /usr/lib/libQtGui.so.4
#25 0xb65cda21 in QWidgetPrivate::show_helper() () from /usr/lib/libQtGui.so.4
#26 0xb65cde61 in QWidget::setVisible(bool) () from /usr/lib/libQtGui.so.4
#27 0xb708a63c in ?? () from /usr/lib/python2.7/site-packages/PyQt4/QtGui.so
#28 0xb65cd978 in QWidgetPrivate::showChildren(bool) ()
from /usr/lib/libQtGui.so.4
#29 0xb65cda21 in QWidgetPrivate::show_helper() () from /usr/lib/libQtGui.so.4
#30 0xb65cd7f5 in QWidgetPrivate::show_recursive() ()

from /usr/lib/libQtGui.so.4
#31 0xb65cd8f9 in QWidgetPrivate::showChildren(bool) ()
from /usr/lib/libQtGui.so.4
#32 0xb65cda21 in QWidgetPrivate::show_helper() () from /usr/lib/libQtGui.so.4
#33 0xb65cd7f5 in QWidgetPrivate::show_recursive() ()
from /usr/lib/libQtGui.so.4
#34 0xb65cd8f9 in QWidgetPrivate::showChildren(bool) ()
from /usr/lib/libQtGui.so.4
#35 0xb65cda21 in QWidgetPrivate::show_helper() () from /usr/lib/libQtGui.so.4
#36 0xb65cde61 in QWidget::setVisible(bool) () from /usr/lib/libQtGui.so.4
#37 0xb72147ec in ?? () from /usr/lib/python2.7/site-packages/PyQt4/QtGui.so
#38 0xb74051d2 in ?? () from /usr/lib/python2.7/site-packages/PyQt4/QtGui.so
#39 0x49fb9daf in PyCFunction_Call (func=
<built-in method show of MainWindow object at remote 0xb7ce5dac>, arg=(),
kw=0x0) at /usr/src/debug/Python-2.7.3/Objects/methodobject.c:116
#40 0x4a0193ba in call_function (oparg=<optimized out>, pp_stack=0xbfffecd4)
at /usr/src/debug/Python-2.7.3/Python/ceval.c:4098
...