Someone on stackoverflow was kind enough to point out my error. My parent method() should have been:

QModelIndex MyModel::parent(const QModelIndex &index) const { if (!index.isValid()) { return QModelIndex(); } QObject *item = (QObject *)index.internalPointer(); Directory *parentItem = qobject_cast<Directory *>(item->parent()); if (!parentItem || parentItem == invisibleTopLevelDirectory()) { return QModelIndex(); } Directory *parentOfParentItem = qobject_cast<Directory *>(parentItem->parent()); if (!parentOfParentItem) { return QModelIndex(); } int listIndex = parentOfParentItem->indexOfItem(parentItem); if (listIndex < 0) { return QModelIndex(); } else { return createIndex(listIndex, index.column(), parentItem); } }

@Chris-Kawa Hi, Thank you for the prompt reply. The bug was in my model as you said, but I think I've found the problem.

It turns out I needed the following:

if(!hasIndex(row, column, parent)) return QModelIndex();

In my "QAbstractItemModel::index()" function. I didn't think the view widget would call "index()" with out of bound row/column combinations since it can use "QAbstractItemModel::rowCount()" and QAbstractItemModel::columnCount()" to get the structure of the model.

Thanks again for your help.