problem with agg

Greetings… I am working using
the matplotlib version 0.90.1, and i am having some strange problems with
my application. When i execute in some pcs, there is no
problem at all, but in others pcs, i receive this message:

File “pylab.pyc”, line 1 in ?
File “matplotlib\pylab.pyc”, line 203 in ?
File “matplotlib\axes.pyc”, line 14 in ?
File “matplotlib\agg.pyc”, line 5 in ?
File “matplotlib_agg.pyc”, line 12 in ?
File “matplotlib_agg.pyc”, line 10 in ?
ImportError: Dll Load Failed

All the pc’s have Windows Xp, most of them Pentium 4, some
are Pentium D. I don’t know what may be the issue. All those
pcs have the same software, just different hardware, i hope
you could help me with this little problem. Thanks in advance…