AJAX Control Toolkit's combobox + IE are too slow

I have problems with optimizing AJAX Control Toolkit. The specific problem is that 4800 records take about 30 seconds to bind in Internet Explorer (only 2 seconds in Opera & Firefox). I've tried anything, but I still can't improve the load time in IE.

I've already enabled compression and caching, I'm using ToolkitScriptManager instead of ScriptManager. I've tried setting LoadScriptsBeforeUI and EnablePartialRendering to false, but it still doesn't help.

This is the query I use for binding.

var osoba =
     from o in db.osobas
     orderby o.osoba_prezime
     select new {
          o.osoba_id,
          person = o.osoba_prezime + " " +
                   o.osoba_ime + " | " +  
                   o.tijelo.tijelo_naziv + " | " +
                   o.radno_mjesto.rm_naziv_m
          };

cb1.DataSource = osoba;
cb1.DataTextField = "person";
cb1.DataValueField = "osoba_id";
cb1.DataBind();
cb1开发者_开发知识库.Items.Insert(0, " ");

Any help would be appreciated. Thank you!

Do you happen to have the developer toolbar open? I've had speed issues in IE when the toolbar is running, and when it's closed, load times are considerably faster.