MySqlException: Expected prepared statement marker

[max m]

Hi
I am using Mysql5 with .Net connector.

===code:
transacion = mcn.BeginTransaction();
command.Connection = connection;
command.Transaction = mtrans;
command.CommandText = "insert into campaign_main(CampaignName) values(?cname);";
command.Parameters.Add("cname", MySqlDbType.VarChar);
command.Prepare();
command.Parameters["cname"].Value = CampaignName.Text;
command.ExecuteNonQuery();

command.CommandText = "select LAST_INSERT_ID();";
datareader = mcmd.ExecuteReader();
datareader.Read();
int ID = datareader.GetInt32(0);

command.CommandText = "insert into campaign_data(CampaignID,CampaignTypeID,Subject,Body) values(?cid,?ctype,?subject,?body);";
//All the queries works fine till the code reaches this prepare statement.
command.Prepare();
=================
when it reached the last command.prepare statement, the Exception is thrown.

===Full stack trace:
[MySqlException: Expected prepared statement marker]
MySql.Data.MySqlClient.NativeDriver.Prepare(String sql, String[] parmNames) +412
MySql.Data.MySqlClient.MySqlCommand.Prepare() +241
CreateCampaign.SaveTextCampaign() in CreateCampaign.aspx.cs:112
CreateCampaign.FinishButton_Click(Object sender, EventArgs e) in CreateCampaign.aspx.cs:84
System.Web.UI.WebControls.Button.OnClick(EventArgs e) +105
System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +107
System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +7
System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +11
System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +33
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +5102
==========

What am i doing wrong?
Why is the exception thrown only in the second prepare statement, when the both prepare statement does the same thing?

I have also tried replacing ? with @