Inserting an image via 3mb via linq-to-sql

New day, new problem :-)

Code:
Client Side:

void abw_Closed(object sender, EventArgs e)
{
    DbServiceClient sc = new DbServiceClient();
    abw = (AddBlobWindow)sender;
    fi = ((AddBlobWindow)sender).fi;
    if ((bool)((AddBlobWindow)sender).DialogResult)
    {
        blob = new Blob();
        binBlob = new Binary();
        binaryBlob = new byte[fi.Length];

        int n = fi.OpenRead().Read(binaryBlob,0,Convert.ToInt32(fi.Length));

        binBlob.Bytes = binaryBlob;
        blob.Content = binBlob;
        blob.Signature = abw.tbSignature.Text;
        blob.Size = (int)fi.Length;

        sc.SaveBlobCompleted += new EventHandler<AsyncCompletedEventArgs>(sc_SaveBlobCompleted);
        sc.SaveBlobAsync(blob);
        }
    }

      

        
        
        
      

    

Server side service code:

[OperationContract]
public void SaveBlob(Blob blob)
{
    try
    {
        RichTekstModelDataContext dc = new RichTekstModelDataContext();
        dc.Blobs.InsertOnSubmit(blob);
        dc.SubmitChanges();
    }
    catch (Exception ex) { string s = ex.Message; }
}

      

        
        
        
      

    

Problem: When I try to save blobs with Content less than 3mb it works fine, but when blob exceeds 3mb I get a "Not Found" exception (---> error line) in the Refernece.cs file

public void EndSaveBlob(System.IAsyncResult result) {
    object[] _args = new object[0];

      

        
        
        
      

    

----> base.EndInvoke ("SaveBlob", _args, result); }

I have no idea how to fix this. I have set in web.config the appropriate buffer sizes, but it doesn't work yet.

Thanks for the help.