On RHEL5 (not Ubuntu 12.04) if you run a Qt application with the Canopy provided Python environment, it will segfault. For example this can happen if you explore the Mayavi pipeline, i.e. if you plot something using mayavi's mlab and then click on the mayavi pipeline you will get a segfault. This could also happen if you click on the "configure subplots" toolbar icon on a matplotlib plot.
This happens because an incompatible style is used by Qt. The workaround is to add a section in:
with the following contents:
You will need to re-start IPython if you are running the application from IPython.