hyphenate.verbatim adds visible hyphens to PDF output

Hi all -

When I have hyphenate.verbatim turned on, my PDF has a visible hyphen 
character before each space.  The hyphens go away if I turn 
hyphenate.verbatim off.

I am using Java 1.4.2, Xerces 2.8.0, Saxon 6.5.5, FOP 0.20.5, and DocBook 
XSL 1.70.1.

With Saxon, the FO output includes a NO-BREAK SPACE (c2 a0) and a SOFT 
HYPHEN (c2 ad) for each space character.  It appears FOP is rendering
this as two visible characters.  Is this a problem with FOP, or Saxon?

FWIW, I didn't notice this problem until I switched to Saxon+Xerces from 
whatever the default JAXP implementations are for JRE 1.4.2.  With the old 
set-up, the FO renders each space character as an ASCII space (0x20). 
(Naturally, this appeared normally in the final PDF.)  I notice turning 
off hyphenate.verbatim causes Saxon to output ASCII spaces, so maybe the 
JRE 1.4.2 default XSLT processor just doesn't support the feature...?

Is this a known issue?  Is the problem in Saxon, or FOP?  Is there a 
work-around that preserves the intended behavior of hyphenate.verbatim, or 
do I just need to live without it?

Thanks!

-- Dan