Using VS2005, dotnet 2.0.
Here's some code which reproduces the issue.

Web Service code :
==
        [WebMethod]
        public string SendDataSet(DataSet ds)
        {
            DataRow dr = ds.Tables[0].Rows[0];

   string sCurrent = (string)dr[0, DataRowVersion.Current];
   string sOriginal = (string)dr[0, DataRowVersion.Original];

            return "current : " + GetStringAsHex(sCurrent) + ", original : " 
+ GetStringAsHex(sOriginal);

        }

        private static string GetStringAsHex(string str)
        {
            System.Text.StringBuilder sb = new 
System.Text.StringBuilder("0x");
            for (int i = 0; i < str.Length; i++)
            {
                sb.AppendFormat("{0:X2}", (int)str[i]);
            }

            return sb.ToString();
        }
==

Run this code on the client end :
==
        private void bDataSetTest_Click(object sender, EventArgs e)
        {
            DataSet ds = new DataSet();
            DataTable dt = ds.Tables.Add("t");
            dt.Columns.Add("Data", typeof(string));

            DataRow dr = dt.NewRow();
            dr["Data"] = "\n";
            dt.Rows.Add(dr);
            dt.AcceptChanges();
            dr["Data"] = "\n";


            HelloWorldWebServiceTestApp.localhost.HelloWorldWebService ws = 
new HelloWorldWebServiceTestApp.localhost.HelloWorldWebService();
            ws.Url = this.tbUrl.Text.Trim();

            string res = ws.SendDataSet(ds);
            MessageBox.Show(res);
        }
==

The messagebox displays :  "current : 0x0A, original : 0x".
I was expecting : "current : 0x0A, original : 0x0A".

So, there seems to be a problem with the original value of columns which 
only contain whitespace. The web method does not see exactly what the client 
has sent.

Any ideas ?
Thanks,
Stephen