"undefined symbol" error message when importing from matplotlib._path


we're running Matplotlib 1.0.0 with Python 2.6.2 on CentOS 5.6. When importing from matplotlib._path, users get an error message

"undefined symbol: _ZSt16__ostream_insertIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_PKS3_l"

I'm at a loss. There were no errors during the installation

Generating the error:

$ python-2.6
Python 2.6.2 (r262:71600, Aug 5 2010, 14:21:11)
[GCC 4.4.4] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from matplotlib._path import affine_transform
Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
ImportError: /g/software/linux/pack/python-2.6/lib/python2.6/site-packages/matplotlib/_path.so: undefined symbol: _ZSt16__ostream_insertIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_PKS3_l
>>> exit()

Anyone has seen this before and/or knows a fix? There are some reports about such an error on the web, but they are all quite old and I cannot relate them to the current issue.

Thanks in advance