Ajax post sometimes removes body and adds NTLM Authorization - ajax

Question

We're experiencing some problems with some ajax calls. On the server side we're running Apache Tomcat with Servlets. On a few calls an Authorization (NTLM) is added in the request header,
and the post body is removed. We are using NTLM authentication on the site, but authentication is already done before these ajax calls are made, and this only happens on certain ajax calls.
Here the JavaScript making the Ajax call.
var postObjects = function(f, parameter, value, variables)
{
var post = {};
post['f']=f;
post['courseid']=trapi.courseID;
post['courseresourceid']=trapi.courseResourceID;
post['mode']=trapi.mode;
if(parameter!=null)
post['parameter']=parameter;
if(value!=null)
post['value']=value;
if(variables!=null)
{
for(var i=0; i<variables.length;i++)
{
post[variables[i][0]]=variables[i][1];
}
}
var returnString="";
$.ajax(
{
url : location.pathname,
data:post,
cache:false,
global:false,
dataType:'text',
contentType:'application/x-www-form-urlencoded; charset=UTF-8',
type:'POST',
async:false,
success: function(data)
{
returnString=data;
},
error: function(jqXHR, textStatus,errorThrown)
{
returnString="Error: "+textStatus;
}
});
return returnString;
}
And here is info from fiddler about a POST made by the postObjects function which adds NTLM authorization:
POST http://localhost:8080/trainweb/courses HTTP/1.1
Accept: text/plain, */*; q=0.01
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
Referer: http://localhost:8080/trainweb/courses?f=courseframe&courseid=909
Accept-Language: nb-NO
Accept-Encoding: gzip, deflate
User-Agent: Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; WOW64; Trident/6.0)
Connection: Keep-Alive
DNT: 1
Host: localhost:8080
Pragma: no-cache
Cookie: JSESSIONID=C18B2FA564626BCEB82C4C3AD8837AE8; FillScreenWidth=0; DefaultSearch=docno; lang=no
Authorization: NTLM BASE64ENCODEDSTRING
Content-Length: 0
And here is info from fiddler about a POST made by the same postObjects function not adding NTLM authorization:
POST http://localhost:8080/trainweb/courses HTTP/1.1
Accept: text/plain, */*; q=0.01
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
Referer: http://localhost:8080/trainweb/courses?f=courseframe&courseid=909
Accept-Language: nb-NO
Accept-Encoding: gzip, deflate
User-Agent: Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; WOW64; Trident/6.0)
Connection: Keep-Alive
Content-Length: 61
DNT: 1
Host: localhost:8080
Pragma: no-cache
Cookie: JSESSIONID=C18B2FA564626BCEB82C4C3AD8837AE8; FillScreenWidth=0; DefaultSearch=docno; lang=no
f=getlasterror&courseid=909&courseresourceid=4079&mode=normal
Do I have to re-authenticate each time this happens?