CLONE -QTreeView expansion/collapsing inside a QComboBox stops working under certain circumstances

We have a control built on top of a QComboBox containing a QTreeView.

If the user tries to either select an item in the QTreeView or open a subtree and while doing so, moves the mouse while still holding down the mouse button (as if, say, to highlight/mark more than one line in the tree view), any subsequent attempt to expand or collapse a subtree will fail - the whole tree view will remain in exactly the state it was before this action, no matter what the user does.

I've attached a simple program that I used to reproduce this behaviour. In order to reproduce it, I used the following steps:

• Select a directory in the directory tree and expand it
• Inside the expanded directory tree, position the mouse over one directory entry
• Now hold down the (left) mouse button and drag the mouse a few entries down (a single entry should be sufficient)
• A this point, collapsing and expanding other parts of the directory tree stops working

#include <QtGui>

int main(int argc, char **argv)
{
    QApplication app(argc,argv);
    QDirModel* model = new QDirModel();
    QTreeView* view = new QTreeView();
    view->setSelectionMode(QAbstractItemView::SingleSelection);
    view->setModel(model);
    QComboBox combo;
    combo.setModel(model);
    combo.setView(view);
    combo.show();
    app.exec();
}