XML Error 1.0 - ???

I have a tiny little xml file with a php parser to read it; the php is opening the xml file fine, but when it comes to actually _read_ it, it's giving me "XML Error 1.0". I've been through every bit of documentation I can find, and can't find what this might mean-- I assume it's something pretty basic from the number! Can anyone enlighten me? The relevent bit of php is while ($data = fread($fp, 4096)) { if (!xml_parse($parser, $data, feof($fp))) { die(sprintf("XML error %d %d", xml_get_current_line_number($parser), xml_get_current_column_number($parser))); } } TIA Sue