Error on page 'Invalid character' once click dropdownlist with AutoPostBack=true

[harmeer]

Hi,
I have a problem with error on page once I click dropdownlist to
select an item.
Details code as below

#HTML page
<EditItemTemplate>
<aspropDownList id=cbReasonIn runat="server" Width="194px"
CssClass="Standard-text" Visible="False" AutoPostBack="True"
OnSelectedIndexChanged="lstItems_SelectedIndexChanged" DataSource="<%#
ListGridReason() %>" DataTextField="REASON_DESCRIPTION"
DataValueField="REASON_ID">

#Code behind
Public Sub lstItems_SelectedIndexChanged(ByVal sender As
System.Object, ByVal e As System.EventArgs)
Select Case sender.SelectedIndex.ToString
Case 9
Dim lblNoTempPass As Label
lblNoTempPass =
CType(gridTA.Items(gridTA.EditItemIndex).FindControl("lblNoTempCard"),
Label)
lblNoTempPass.Visible = True
Case 13
Dim txtNoteIn As TextBox
txtNoteIn =
CType(gridTA.Items(gridTA.EditItemIndex).FindControl("txtNoteIn"),
TextBox)
txtNoteIn.Visible = True
End Select
End Sub

This error only happen in windows 2003, it was tested under windows XP
& windows 2000 and working.

Someone please help!!!!

Thank you in advanced.
MeeR