500 error with microsoft translator TranslateArray

I keep getting 500 errors when I post my xml, but everything looks fine, can someone check my request?

POST /V2/http.svc/TranslateArray HTTP/1.1

User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.64 Safari/537.31
Host: api.microsofttranslator.com
Accept: */*
Accept-Encoding: gzip,deflate,identity
Referer: https://datamarket.accesscontrol.windows.net/v2/OAuth2-13
Content-Type: text/xml; charset=UTF-8
Authorization: Bearer http%3a%2f%2fschemas.xmlsoap.org%2fws%2f2005%2f05%2fidentity%2fclaims%2fnameidentifier=PtvGuide&http%3a%2f%2fschemas.microsoft.com%2faccesscontrolservice%2f2010%2f07%2fclaims%2fidentityprovider=https%3a%2f%2fdatamarket.accesscontrol.windows.net%2f&Audience=http%3a%2f%2fapi.microsofttranslator.com&ExpiresOn=1374031980&Issuer=https%3a%2f%2fdatamarket.accesscontrol.windows.net%2f&HMACSHA256=4jA7EKDQkhf4UGRLwaD7pumODV0lwDRDI%2fXnthAB8B0%3d
Content-Length: 223

<?xml version='1.0'?>
<TranslateArrayRequest>
  <From>de</From>
  <Texts>
    <string xmlns="http://schemas.microsoft.com/2003/10/Serialization/Arrays">guten</string>
  </Texts>
  <To>en</To>
</TranslateArrayRequest>