multi_xml_bug.rb

require "multi_xml"
# copy paste above xml document to `xml` variable

MultiXml.parser
# => MultiXml::Parsers::Ox
MultiXml.parse(xml).keys
# => ["aws:UrlInfoResponse"]
MultiXml.parser = :rexml
# => :rexml 
MultiXml.parse(xml).keys
# => ["UrlInfoResponse"] 

response.xml

"<?xml version=\"1.0\"?>\n<aws:UrlInfoResponse xmlns:aws=\"http://alexa.amazonaws.com/doc/2005-07-11/\"><aws:Response xmlns:aws=\"http://awis.amazonaws.com/doc/2005-07-11\"><aws:OperationRequest><aws:RequestId>85b89e85-8579-74d4-f88d-33bbb4e4d536</aws:RequestId></aws:OperationRequest><aws:UrlInfoResult><aws:Alexa>\n  \n  <aws:ContactInfo>\n    <aws:DataUrl type=\"canonical\">dupa.com</aws:DataUrl>\n    <aws:PhoneNumbers>\n      <aws:PhoneNumber>602 741 670</aws:PhoneNumber>\n    </aws:PhoneNumbers>\n    <aws:OwnerName>WebFabrika</aws:OwnerName>\n    <aws:Email>wlochaty@dupa.com</aws:Email>\n    <aws:PhysicalAddress>\n      <aws:Streets>\n        <aws:Street>Ul. Grzybowska 9 m.1419</aws:Street>\n      </aws:Streets>\n      <aws:City>Warszawa, Woj. Mazowieckie 00-132</aws:City>\n      <aws:Country>POLAND</aws:Country>\n    </aws:PhysicalAddress>\n    <aws:CompanyStockTicker/>\n  </aws:ContactInfo>\n  <aws:ContentData>\n    <aws:DataUrl type=\"canonical\">dupa.com</aws:DataUrl>\n    <aws:SiteData>\n      <aws:Title>WebFabrika</aws:Title>\n      <aws:OnlineSince>01-Mar-1999</aws:OnlineSince>\n    </aws:SiteData>\n    <aws:Speed>\n      <aws:MedianLoadTime/>\n      <aws:Percentile/>\n    </aws:Speed>\n    <aws:AdultContent>no</aws:AdultContent>\n    <aws:Language>\n      <aws:Locale>pl</aws:Locale>\n      <aws:Encoding>iso-8859-2</aws:Encoding>\n    </aws:Language>\n    <aws:LinksInCount>28</aws:LinksInCount>\n    <aws:Keywords/>\n    <aws:OwnedDomains/>\n  </aws:ContentData>\n  <aws:Related>\n    <aws:DataUrl type=\"canonical\">dupa.com</aws:DataUrl>\n    <aws:RelatedLinks>\n      <aws:RelatedLink>\n        <aws:DataUrl type=\"canonical\">www.promail.pl/</aws:DataUrl>\n        <aws:NavigableUrl>http://www.promail.pl/</aws:NavigableUrl>\n        <aws:Title>www.promail.pl/</aws:Title>\n      </aws:RelatedLink>\n    </aws:RelatedLinks>\n  </aws:Related>\n  <aws:TrafficData>\n    <aws:DataUrl type=\"canonical\">dupa.com</aws:DataUrl>\n    <aws:Rank>8776627</aws:Rank>\n    <aws:RankByCountry/>\n    <aws:RankByCity/>\n    <aws:UsageStatistics>\n      <aws:UsageStatistic>\n        <aws:TimeRange>\n          <aws:Months>3</aws:Months>\n        </aws:TimeRange>\n        <aws:Rank>\n          <aws:Value>8776627</aws:Value>\n          <aws:Delta>+963196</aws:Delta>\n        </aws:Rank>\n        <aws:Reach>\n          <aws:Rank>\n            <aws:Value>7526764</aws:Value>\n            <aws:Delta>+885439</aws:Delta>\n          </aws:Rank>\n          <aws:PerMillion>\n            <aws:Value>0.12</aws:Value>\n            <aws:Delta>-20%</aws:Delta>\n          </aws:PerMillion>\n        </aws:Reach>\n        <aws:PageViews>\n          <aws:PerMillion>\n            <aws:Value>0</aws:Value>\n            <aws:Delta>-20%</aws:Delta>\n          </aws:PerMillion>\n          <aws:Rank>\n            <aws:Value>11417545</aws:Value>\n            <aws:Delta>984027</aws:Delta>\n          </aws:Rank>\n          <aws:PerUser>\n            <aws:Value>1</aws:Value>\n            <aws:Delta>0%</aws:Delta>\n          </aws:PerUser>\n        </aws:PageViews>\n      </aws:UsageStatistic>\n    </aws:UsageStatistics>\n    <aws:ContributingSubdomains/>\n  </aws:TrafficData>\n</aws:Alexa></aws:UrlInfoResult><aws:ResponseStatus xmlns:aws=\"http://alexa.amazonaws.com/doc/2005-07-11/\"><aws:StatusCode>Success</aws:StatusCode></aws:ResponseStatus></aws:Response></aws:UrlInfoResponse>"