debugging python code


I tried to use matplotlib with numarray instead of numeric for the
first time, but it seems that it fails for me even for the simplest
examples. For example the script

    from matplotlib.matlab import *
    from math import sin

    x=map(lambda tt:sin(tt), t)


fails during the savefig call with a floating point exception.
Unfortunately there is no backtrace printed, so I have no idea where
exactly the problem lies.

Questions: Is there any easy way to get more information about where
the failure happens? Is this specific problem known?

All the best,