Strange Python internal error

[JKPeck]

We have a user on Windows with Python 2.6 who gets this error message when executing an import statement.
    from extension import Template, Syntax, processcmd 
SystemError: ..\Objects\listobject.c:169: bad argument to internal function

The module can be imported directly via
import extension
with no problem.  And large numbers of other users execute this same code with no problem.

Does anybody have a clue as to how this might arise?

TIA,
Jon Peck