[plt-scheme] ProfessorJ difficulties

Using the latest exp-tagged DrScheme, I'm getting the following error
whenever I try to compile or run a ProfessorJ program (in the Full
language level):

dir-path-path: expects argument of type <struct:dir-path>; given (#<path:.>)

The file itself is simple (a duplicate of the Posn class, in fact) and
it works fine in v208.  I'm building on Mac OS X v10.3.6.  Does anyone
know what the problem might be?

--Carl