[plt-scheme] Having trouble getting Tex2Page working...

My scheme directory containing tex2page is in my path.  I go to the
directory containing a sample tex file (story.tex), and type:
tex2page story
at the prompt, and get the following error:

This is TeX2page, Version 20070609 (MzScheme 372, windows)
file-exists?: expects argument of type <path or string>; given #f


Any idea what's going on?  I've tried other formulations, explcitly
giving the file's directory, for example, but with no success.

Thanks,

Mark