Which latest version? 2.49A, the latest official 2.5 beta, or the latest 2.5 SVN build? Do you have the correct version of Python installed and is Blender finding it correctly? Exactly what error are you getting? Is the geometry messed up or does it simply refuse to open? If its a python error, what does the error message…
What version of Blender are you using? IIRC Blender uses Python for the import modules. Make sure that you have the correct version of Python installed. I vaguely remember that some early versions of 2.5 had some issues with importers due to the API being in heavy flux, but otherwise I've never had trouble with it. In fact…