Moved my ASP.NET app to a Windows 2008 server, now DropDownList SelectedIndexChanged events don't fire

Existing ASP.NET 2.0 app,currently deployed on a Windows Server 2003 machine.

Testing moving it to a new WS 2008 开发者_JAVA百科box. App loads fine, other behavior seems fine, but I'm not getting OnSelectedIndexChanged events from my DropDownLists.

I guess I could add command buttons and run the code in the button click event based on the Item selected in the dropdown but that seems kinda clunky.

Any thoughts?

EDIT- The controls are stand-alone on the form. Not part of a datagrid/gridview or any other container control.

<asp:DropDownList ID="ddlOCA" runat="Server" OnSelectedIndexChanged="ddlOCA_SelectedIndexChanged" AutoPostBack="true"></asp:DropDownList>

EDIT 2 - This Windows 2008 server is 64 bit, whereas the other server where I do get the events is 32 bit.

EDIT 3 - On the WS 2008 machine, there are also several that no longer fire (collaps/expand). Sigh.

A few ideas:

1. Though this seems like a long shot, are you missing an IIS header that is forcing IE8 to run in compatibility mode?
2. Have you installed ASP.NET v2.0 (I can't remember if this is pre-installed or not)? Make sure you check carefully as some of the libraries will come with ASP.NET v3.5 but I don't believe that gives you everything.
3. Does the user running the app is IIS have the necessary security rights? You might want to run aspnet_regiis with the -ga option if you aren't sure (this won't hurt anything if you run it a second time).

This is an intranet app. Added the site to the trusted sites for the Local Intranet in IE.