I'm 64-bit Windows 7 with matplotlib 1.2.0 and WxPython 220.127.116.11. I was fiddling around with some of the different backends to see what they look like and I found that the WxAgg backend doesn't work:
Python 2.7.3 (default, Apr 10 2012, 23:24:47) [MSC v.1500 64 bit (AMD64)] on win
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>>> import matplotlib as mpl
>>> from matplotlib import pyplot
>>> pyplot.plot([1, 2, 3])
[<matplotlib.lines.Line2D object at 0x0000000006757DA0>]
When I do the plot, the figure windows appears, but it's blank (without even a proper blank background, just a white area) and immediately shows "Not responding". I have to kill the window, and doing so crashes the Python session. However, it works without the "ion()" call: I can then call show() and see the plot fine.
I have wxPython working fine in other apps. In fact, what's especially odd is that I actually have an app that directly uses FigureCanvasWxAgg to embed matplotlib graphs in a GUI, and this seems to work fine. So it seems the problem is somehow in matplotlib's own management of the interactive figure window.
There was a previous question about a similar WxAgg issue on the list ( http://matplotlib.1069221.n5.nabble.com/trouble-with-show-not-drawing-in-interactive-mode-w-WxAgg-td39110.html ), but there was no real answer: the poster just decided not to use WxAgg. But aren't we really supposed to be able to use WxAgg interactively?
"Do not follow where the path may lead. Go, instead, where there is no path, and leave a trail."