When using QFileDialog two problems were noticed:

1) While browsing across different directories, if you select a file and
move to another directory, that file name does not get cleared from
'File name' text box.
2) If you delete file name from text box, the Open button does not get
disabled. It gets disabled only when you move to some other directory.

This was found to happen on X11 4.4.0, 4.4.3, and 4.5 snapshot