TypeError: 'module' object is not callable

[Forafo San]

I wrote a class, Univariate, that resides in a directory that is in my PYTHONPATH. I'm able to import that class into a *.py file. However when I try to instantiate an object with that class like:

x = Univariate(a)             # a is a list that is expected by the Univariate class

python raises the TypeError: 'module' object is not callable.  If I embed the code of the Univariate class in my *.py file, there is no problem.  Also, when the class is imported and I do a

print dir(Univariate)

it does not print all the methods that are in the class, while if the class code appears in my *.py file, all the methods are available and a list with the correct methods are printed.

What gives?

Thanks in advance.
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FreeBSD 7.2 machine with python version 2.5.6