Hmm, I had problems with PyQt.QtGui.QFileDialog stuff before, as mixed up strings and timestamps for files. With the installed app they seem to work now ok. Only thing that comes to my mind is the custom theme (altough I have one also, ubuntu theme). If you want you could give it a spin with the default themes.

Before that please check if you have python2.5-qt4-maemo5 package installed. I don't have it as a dependency yet and in code its optional. I have changed this now and it will be a new dep in the next release. I'm not sure if that is needed for the file dialogs, but those are maemo spesific things that pop up. But I guess they call some gtk stuff from PyQt.QtGui.QFileDialog, at least I get gtk assert fails for timestamps when running in scratchbox x86 emulator.

Try sudo gainroot; apt-get install python2.5-qt4-maemo5; and give it another go, doubt it helps though as the gui package would have that as a dependency. Also you could try to run from terminal so you will get python error prints if something goes sideways: cd /opt/dropn900; ./dropn900.py;