stowite;
I changed the expression from "(0[xX])?([0-9a-fA-F][0-9a-fA-F])+"
to "0?[xX]?([0-9a-fA-F][0-9a-fA-F])+" and then it worked!
I didn't really need the capture i.e. the parens around '0[xX]'.
I might just go the route suggested by MarkT if I can figure out what he's talking about (i.e. 'hope').
I'm thinking it's a typo but I can't think what it would be correctly -- nothing comes to mind that sounds or looks like 'hope' that relates to parsing text.
Thanks for the help.
Ray