error reading xml config values:http://admin50plus.buchungskalkulator.at/xml/export/accountInfo.php?accountId=0&contactTypId=26

exception 'Zend_Config_Exception' with message 'simplexml_load_file(http://admin50plus.buchungskalkulator.at/xml/export/accountInfo.php?accountId=0&contactTypId=26): failed to open stream: HTTP request failed! HTTP/1.0 500 Internal Server Error simplexml_load_file(): I/O warning : failed to load external entity "http://admin50plus.buchungskalkulator.at/xml/export/accountInfo.php?accountId=0&contactTypId=26"' in /home/lib/public_html/Zend/Config/Xml.php:98 Stack trace: #0 /home/sites/50plus.buchungskalkulator.at/public_html/lib/calculator/config.php(41): Zend_Config_Xml->__construct('http://admin50p...', 'accounts') #1 /home/sites/50plus.buchungskalkulator.at/public_html/kalkulator/config.php(234): calculator_config->getConfig(Array) #2 /home/sites/50plus.buchungskalkulator.at/public_html/kalkulator/index.php(16): include('/home/sites/50p...') #3 {main}