That's weird, the XML seems to parse OK for me. Could you provide an example of data that trips the parser? As it is I really can't see how a ' could cause any problem.

For the record, I doubt very much that expat is the problem. It was written by James Clarke, who was one of the main author of XML, and who is quite famous for the quality of the tools he writes (troff, nsgmls, jade, expat). Actually expat is probably _the_ XML reference parser. If expat says it's not well-formed then you can assume it is not.