Are you using Jaunty by chance? Now that I think about it there is a conflict on Jaunty. PyQt 4.4 and Qt 4.5 cause the viewer to segfault.
Comment out the line:
Code:
self.view.setUrl(QtCore.QUrl("about:blank"))
in the main_ui.py file for the viewer. I'm not 100% sure where it gets installed to.