any css gurus out there up for a challenge?

Ok, my designer and I have been trying to fix this for a couple of days and can't figure out what we've got wrong - when you go to this site http://tsbcomplete.com/nwpropertypreservation/ the top horizontal nav bar "jumps". It starts on the left and then moves into position... any css experts in this group that can see the problem and give me a heads up?

Thanks
Harmony