simplexml choking on apparently valid XML

Hey all - I'm using simplexml-load-string just to validation a string of XML, and libxml-get-errors to return any errors. It's always worked before, but today it's choking on this line in the XML: <client_orderitem_number>Basketball Personalized Notebook - Jeff&apos;s</client_orderitem_number> It's returning "Premature end of data in tag client_orderitem_number line 90" but as far as I can tell, Jeff&apos;s is properly XML encoded. I can't debug this. Any suggestions? I have run the XML through a couple of online validators and it does come back as valid with no errors found.