Can only preview the latest customized report..What's wrong?

[beginner81]

I have 2 button on form1 named "CustomizedReport" and "LoadReport" Button respectively.
At first, I click at "CustomizedReport" button to customize a report(report1) and save it
to C:\report1.repx. Then i click at "LoadReport" button to load and preview the report1.repx
and it's work fine. After that i click at "CustomizedReport" button again to design report2.repx
and again save it to C:\report2.repx. After that i click at "LoadReport" button to load report2.repx and
again it works fine here. But when i try to load the report1.repx(first customized report) error message prompt out as following:

"An unhandled exception of
type 'DevExpress.XtraReports.Serialization.XRSerialization' occured in
devexpress.xtrareports.dll

Addtional information: An error occurred during deserialization -
possible wrong report class name"


The following is the code for "CustomizedReport" button and "LoadReport" button.


private void buttonCustomizedReport_Click(object sender, System.EventArgs e)
{
XtraReport1 rpt = new XtraReport1();
rpt.RunDesigner();
}


private void buttonLoadReport_Click(object sender, System.EventArgs e)
{
OpenFileDialog openFileDialog1 = new OpenFileDialog();
openFileDialog1.InitialDirectory = "c:\\" ;
openFileDialog1.Filter = "repx files (*.repx)|*.repx";
openFileDialog1.FilterIndex = 2 ;
openFileDialog1.RestoreDirectory = true ;

if(openFileDialog1.ShowDialog() == DialogResult.OK)
{
XtraReport1 rep = new XtraReport1();
rep.LoadState(openFileDialog1.FileName);
rep.SetDataSource(this.getDataSource);
rep.ShowPreview();
}

}


Hope someone can help me as this is quite an important part of the program thanks.