Hi PhotoJoe and Welcome to WebmasterWorld!
don't know as I can help any.. my question would be what Operating Systems are they using?
I have heard that IE7/Vista can render unexpectedly different than IE7/XP/2000 etc
The whitespace in lists (spaces in your vertical menu) has been a sporadic IE problem since IE5, it appears in some versions though has different triggers, whitespace in the HTML (or HTML comments) is sometimes a factor.. if it turns out to be a different OS that's causing it to come back in IE7 then I'd try a look for the usual fixes.
the horizontal scroll is very likely also one of IE's positioning things, i.e. are you using a negative text-indent or negative left/right position for any of your effects?
again it's ODD, but IE7 was always a transition and if Microsoft did have to tweak it for Vista then I don't think there's much can be done seeing as Vista itself and CSS Support for IE8 are very much in limbo.. and without access to two testing platforms it would be hard to troubleshoot. (I'm sticking with my XP for now!)
perhaps refining your search to something like [IE CSS difference Vista XP] will throw some more light?
anyway it sounds to me like your tutor shouldn't fail this assignment as you've obviously checked your stuff, IMHO anyway, especially if it turns out to be a OS problem!
Good Luck and let us know if you track the problem
[edited by: SuzyUK at 7:21 am (utc) on July 13, 2008]