XML_Serializer - unserialize() choking

I'm trying to use XML_Serializer to unserialize some XML into an array. I've installed XML_Parser, XML_Util and XML_Serializer. Whenever I call the unserialize() method while passing a string, everything stops. I don't get any PHP errors with error_reporting(E_ALL) and I don't get any PEAR errors either. Using echo statements I've found that it hangs whenever PHP gets to $status = $unserializer->unserialize($xml); I've tried different XML, I've tried half a dozen tutorials verbatim and it always stops at unserialize() with no errors of any kind. There is no problem with serialize(), though. Is there something at the server or configuration level that would prevent the unserialize() method from working? It is running on a shared server. - Erik Heerlein