movieClipLoader problem!

i have a main movieclip that loads 7 other movieclips. two of them will randomly cause my program to just stop functioning (especially in internet explorer). what happens is ill click a button, my movieClipLoader will start my preloader but then my preloader immediately goes away and nothing works after that.

heres the link if you want to see what im talking about.
http://administration.ucok.edu/roadtogreatness/index2.htm

the contact and registration links seem to make it happen most often. any help would be greatly appreciated.