Closed Issue: MaskedEditExtender (*): Can't highlight or Select text in textbox associate with MaskedEditExtender [25078]

I can't seem to select (or highlight) the text in the textbox that is associate with the MaskedEditExtender. I create an user control that has the following code and put the user control inside an update panel.

<asp:TextBox ID="txtSikwh" onkeypress="return CkKeyPress(event);" onchange="PriorYearCalculated();" Text="<%# AdjustmentValue.SiKwh %>" runat="server" OnTextChanged="txtSikwh_TextChanged"></asp:TextBox>

<cc1:MaskedEditExtender ID="MaskedEditExtender5" runat="server" InputDirection="RightToLeft"
Mask="999,999,999" MaskType="Number" TargetControlID="txtSikwh" AcceptNegative="Left" AutoComplete="false">
</cc1:MaskedEditExtender>

Does anyone has fix for this?

Thanks!