ASP DropDownList UpdatePanel IE JS Errors

I'm getting a peculiar javascript error with IE.
I have an updatepanel, and inside it a drop down list. When I change the dropdownlist's value, it gives me error "Line: 5 '__EVENTTARGET' is null or not an object'.
I took a look, and this Line 5 and __EVENTTARGET are in the ASP.NET generated javascript code.

I want a dropdownlist that fires method when new option selected, with no page flicker.

Here's some of my code :

<asp:ScriptManager ID="uxScriptMan" runat="server" />
<asp:UpdatePanel ID="uxtestupdatepanel" runat="server">
<ContentTemplate>
<asp:DropDownList ID="DropDownList1" runat="server" 
    AutoPostBack="true" OnSelectedIndexChanged="TESTMETHOD">
 <asp:ListItem Text="TEST" Selected="true" />
 <asp:ListItem Text="Yes" Value="1" />
 <asp:ListItem Text="No" Value="0" />
</asp:DropDownList>
</ContentTemplate>
</asp:UpdatePanel>

and

protected void TESTMETHOD(object sender, EventArgs e) { /*do nothing*/ }

In Firefox, it works, no errors. And in fact, on dev machine, uncompiled soln with .aspx and .aspx.cs files, no errors in IE. On production machine, compiled, I get IE js errors.

Whats the problem, how do i fix, or at least, where can I start looking? Done a ton of googling with not much luck.