cross-platform network file paths

Is such a thing even possible?  I have a solution with a calc field,
result is a container.  The calc creates the filepath and name, which
resolves to a network share.  The Windows users can see the image no
problem, but the Mac users cannot.  I've made sure that the Mac is
logged on to the Windows share independent from FMP.  I've tried the
"imagewin:" prefix (Windows path) and the "image:" prefix
(cross-platform path), no luck either way.  It says in FMP Help that
network paths only work on Windows shares, not Mac shares.  But it
doesn't say anything about Windows shares not being accessible from a
Mac client.

Any clues?

thanks

-- 
FW

FileMaker Pro Advanced 8.5 on Windows XP Pro SP2
FileMaker Server 8.0 on Windows 2003 Server R2