In webforms, there's always this kind of prefixing to avoid naming collisions. My first approach to this scenario was to strip the prefix. It worked, but it was too much overhead. I ended up wrapping my control in Div and working my way inside it.

Cheers guys, I always forget about ClientID :) Here's the code, I couldn't use RegisterClientBlock as Sys. had not been loaded.

                if (!Page.ClientScript.IsStartupScriptRegistered("DDEFix"))
                {
                    string ddeFix = "function DDE_pageLoad(){$find('" +
                        DDE.ClientID +
                        "').unhover = doNothing; $find('" +
                        DDE.ClientID +
                        "')._dropWrapperHoverBehavior_onhover();}function doNothing() {}" +
                        "Sys.Application.add_load(DDE_pageLoad);";


                    Page.ClientScript.RegisterStartupScript(this.Page.GetType(), "DDEFix", ddeFix,true);
                }

There you go :) Cheers guys.