[vtkusers] events freeze X using vtk with wxPython

[Eric Boix]

	Dear John,

	Your script runs without any X11 freeze on my RHL 6.1.92 (Piglet),
with Python2.1.1 and wxPython-2.3.1-1. Resizing of window is ok but
refreshing doesn't (window from back to front). BUT I never obtain
the Pan function to be called back when left clicking as could be expected
from EVT_LEFT_DOWN(self, self.pan).
	We also experienced some obscure X11 crashes when running VTK+wx
when the Nvidia driver of our Gforce graphic board were not mature enough
(read really buggy). If you are using a GForce I would strongly recommend
to upgrade your driver to a version greater than 1.0.

	Yours,
	Eric Boix