WCF service taking userPincipleNname instead of passed in string as argument - wcf

Question

This is a weird issue. I am passing in strings into my service, and that string would be the username of the person logged into my website (via windows authorization). I get the string from my website using
HttpContext.User.Identity.Name.ToString()
I parse it from the domain and just get the user Identity. And then I call a wcf service whose contract is similar to this...
generalWCFContractImplementation(string userID);
Now, you would think it would pass in the string that I sent it... However, that is indeed not the case. After doing some debugging, I found out that the string that is being passed in is the userPrincipleName that I am using to setup the WCF connection! Now why on earth would it do that? I am checking all throughout my code to see if accidentally change the userID in some way, but I check as soon as I enter the function what the value of the ID is, and it is the userPrincipleName! I am extremely confused about what is going on here. Does anybody have any idea why that would occur? and how can I remedy that?
Thanks.
UPDATED with code
public string GetOwnedPopulations(string userID)
{
Log.TraceEvent(System.Diagnostics.TraceEventType.Information, string.Format("Entered Method GetOwnedPopulations() CallerNameOnly: {0}, userID: {1} CallerNameOnly==userID {2}", CallerNameOnly, userID, CallerNameOnly == userID), "General");
this.CallerFullDomain = userID;
this.CallerNameOnly = userID;// this.CallerFullDomain.Substring(this.CallerFullDomain.IndexOf('\\') + 1);
string ans;
Log.TraceEvent(System.Diagnostics.TraceEventType.Information, string.Format("Entered Method GetOwnedPopulations() CallerNameOnly: {0}, userID: {1} CallerNameOnly==userID {2}", CallerNameOnly , userID, CallerNameOnly==userID), "General");
searchPopulationbyOwner oReq = new searchPopulationbyOwner();
oReq.ownerName = this.CallerNameOnly;
try
{
StringBuilder sbBuffer = new StringBuilder();
PopulationManagementClient client = UPMC.ISD.EADIS.PopulationManagement.PopManSvc.Utils.GetClient(this.CallerNameOnly);
searchPopulationbyOwnerResponse resp = client.searchPopulationbyOwner(oReq);
Log.TraceEvent(System.Diagnostics.TraceEventType.Information, string.Format("Getting Null Values?: {0}", (resp == null ? ans="yes" : ans="no")), "General");
XmlSerializer xs = new XmlSerializer(typeof(Population[]));
System.IO.StringWriter sw = new System.IO.StringWriter(sbBuffer);
xs.Serialize(sw, resp.populationList);
string sPopulationtXML = sbBuffer.ToString();
return sPopulationtXML;// client.searchPopulationbyOwner(oReq);
}
catch
{
throw;
}
}
As you can see, I pass in the username, and I then set the object that I am going to pass in equal to the user ID. The thing is, userID is either the applicationPoolID, but I am guessing more than likely it is the userPrincipleName (which would happen to be the same as the applicationPoolIdentity... I am not sure if they have to be the same or not). But this is very weird. I have know idea why on earth that would be passed in and not the actual username... And yes, I have looked at my site to see what is being passed in, and it is indeed, the userID... When it hits the service however, it is the userPrincipleName.
Confused?????