MatplotLib errors

[Thomas Philips]

I have just started using MatPlotLib, and use it to generate graphs
from Python simulations. It often happens that the graph is generated
and a Visual C++ Runtime Library error then pops up: Runtime Error!
Program C:\Pythin25\Pythonw.exe   This application has requested the
Runtime to terminate in an unusual way. Please contact the
application's support team for more information.

I'm running Python 2.5.2 under Windows XP. Any thoughts on what what
may be causing the problem?

Thanks in advance

Thomas Philips