RadScriptManager Error

[Srujan]

Hi ,

I have included Radscript manager in my sharpeoint webpart , when I hover te cursor on any of the top or left hand menu items of sharepoint site I am getting error as "Microsoft JScript runtime error:Object expected" ,can any one suggest as how to go about the same,please find the code block below

        protected override void OnLoad(EventArgs e)
        {
                base.OnLoad(e);
                ScriptManager scriptManagerchecknow = ScriptManager.GetCurrent(this.Page);
                if (scriptManagerchecknow == null)
                {
                    scriptManagerchecknow = new RadScriptManager();
                    this.Controls.AddAt(0, scriptManagerchecknow);
                 }
          }
Regards
Srujan.N