Ok - we got a file upload control

Code:
<div style="text-align:center; vertical-align:middle"><asp:FileUpload ID="SourceFileUpload" EnableViewState="true" runat="server" /></div>
It's got EnableViewState as true.

And then this checkbox

Code:
<asp:CheckBox ID="StandardCheckBox" AutoPostBack="true" Text="Yes" EnableViewState="true" runat="server" /></div>
And then this sub

Code:
    Protected Sub CheckBox1_CheckedChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles StandardCheckBox.CheckedChanged
        'FindControl("TransDead").Visible = False
        If StandardCheckBox.Checked Then
            TranslationDeadline.Text = "Standard Turnaround"
        Else
            If TranslationDeadline.Text = "Standard Turnaround" Then
                TranslationDeadline.Text = ""
            End If
        End If
    End Sub
If you browse for a filename prior to click this check box then when you click the check box the filename gets cleared.

What is causing that?