QTreeView and QDirModel Header Sort Question

I'm using a QTreeView with the QDirModel to display files contained in a specific directory. I would like to use the Header sorting capabilities to sort on the filename or date/time columns. However, when ever I try to change the sorting the using the header the view shows the root system disks. I've look though this community site and the QT documentation but nothing I've found explains how to get around this issue.

I'm using QT 4.2.3 on windows XP.

Thanks in Advance!

Do you use QSortFilterProxyModel?