Calendar Extender Problem in asp.net 2.0

[silpa]

Hi,
I have a problem with calendar extender.

Example:
<asp:ScriptManager ID="ScriptManager1" runat="server">

</asp:ScriptManager>

<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>

<img id="a" src="../images/arrowleftmonth.gif" runat="server" />

<cc1:CalendarExtender ID="CalendarExtender1" runat="server" Format="MM/dd/yyyy" TargetControlID="TextBox1" PopupButtonID="a">

</cc1:CalendarExtender>


Problem
The above example is I have a textbox, an <img> tag and Calendar extender.When I click <img> the Calendar will open and after selecting date,the date will be displayed in textbox. This works fine.(This works fine when the textbox is empty when page loads)

My doubt is

I displayed date into the textbox from the databse when page loads.That means if the textbox contains a predefined value when page loads, and now if I click <img> to open calendar to change the date, the calendar is not opened.

I am getting javascript error: Object doesn't support this property or method.

Can u plz tell me how to solve this.

Thanks,

Silpa