caps on errorbar

hi, i'm using the exact code pasted below, and copied from:

i see the vertical error lines, but i'm not able to see the 'cap' as
in the codex above, i've tried changing a few parameters in my
matplotlibrc as well as
different backends.
i'm running matplotlib checked out from svn today. is there something
i can try to make the caps appear?

from pylab import *

t = arange(0.1, 4, 0.1)
s = exp(-t)
e = 0.1*abs(randn(len(s)))
f = 0.1*abs(randn(len(s)))
g = 2*e
h = 2*f

errorbar(t, s, e, fmt='o') # vertical symmetric