ModalPopup cause lost of css on another control

how did you launch the modal popup?

It's Target is an asp:button, the PopupControl is a div. Our ScriptManager is EnablePartialRendering=true. Our Menu (telerik) lost is CSS when we cancel or ok the ModalPopup. (Cancel and Ok are asp:button).

Note. Our ModalPopup has an UpdatePanel embedded in it.

does any of your code perform a Response.Write() during a postback?

No Response.Write. But...

There is a if(Page.ClientScript.IsRegistered...) Page.ClientScript.RegisterScriptBlock(...). Yes, our JScript are between CDATA.