[xsl] Unicode characters being replaced with ??

[dvint@xxxxxxxxx]

I've got an odd problem related to characters like a non breaking space,
plus minus and copyright symbols that have been entered as actual Unicode
values rather than entity references. I'm running a DITA environment on a
Linux server and the pages that are being generated have '??' substituted
as hard characters in the HTML output.

This process has been running fine on a different Linux box and on my
local PC. What has changed are the following things:
- updated Centos
- updated Java
- updated DITA open tool kit

I've seen where output I generate with Unicode characters will sometimes
display in an ASCII editor with some sort of box character, but never a
situation where the actual output has been changed like this. My thought
is that there is some environment setting that is a affecting the way the
stylesheets are producing output.

Has anyone come across this before?

..dan