Problem with ÆØÅ characters when using http headers (Web API)

In my ASP.Net Web Api I have a Get function where input info is sent in the http header. It works fine, except when the http header contains Norwegian characters like Æ, Ø and Å. This characters is transformed to æ ø Ã¥. When the same characters (Æ,Ø,Å) are sent as parameters in the URL it works fine. When testing the script on my local PC it works fine to send Æ, Ø and Å in the http header as well.

I don't know why norwegian characters can't be sent in the http header, but I guess this is an encoding / charset problem. After hours of testing I still can't find any way fo fix it.

Web.config:

<globalization fileEncoding="utf-8" requestEncoding="utf-8" responseEncoding="utf-8" culture="nb-NO" uiCulture="nb-NO" />

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Getting Http Header:
 

private string GetHeader(string key)
{
    var header = "";
    if (Request.Headers.Contains(key))
    {
        IEnumerable<string> values = new List<string>();
        Request.Headers.TryGetValues(key, out values);
        if (!string.IsNullOrEmpty(values.First())) header = values.First();
    }
    return header;
}
 
var headerUserName = GetHeader("UserName");

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Request headers

User-Agent: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.64 Safari/537.31
UserName: ÆØÅ
Accept: */*
Accept-Encoding: gzip,deflate,sdch
Accept-Language: en-US,en;q=0.8
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
 

Response headers

Date: Wed, 15 May 2013 12:46:19 GMT
Server: Microsoft-IIS/6.0
X-Powered-By: ASP.NET
X-AspNet-Version: 4.0.30319
Cache-Control: no-cache
Pragma: no-cache
Expires: -1
Content-Type: application/json; charset=utf-8
Content-Length: 4174