It appears that you don't have a system rigs page (you should get one...they're cool to have), so I can't tell anything about your system, but I'll guess you don't have the latest and greatest system, so it's probably the fading animation that is slowing down your menus. This is easy to disable (w/o installing TWEAKUI). Get the "Display Properties", go to "Effects", and uncheck "Use transition effects for menus and tooltips". HTH.