Matplotlib crash error on mac

Question

I can't run matplotlib on python 2.7. For example:

from pylab import * 
x  = arange(-10.0, 10.0, 0.1)
y = sin(x)
plot(x,y)

is able to run.

but

from pylab import *
x  = arange(-10.0, 10.0, 0.1)
y = sin(x)
plot(x,y)
show()

is not. The show() function cannot run.

Any ideas?