Hello Adam - Toronto
IE for the Mac uses an IE 4 core. Could seems incredible, but true. You can easily reproduce the issues (and therefore : correct them) on your PC by using an IE4 version.
I have the same issue, one of my main clients also still uses IE on the Mac. Hence I use a special mod version of IE, which can be instantly installed/uninstalled on a PC together with any other newer official version.
Should you need it, here is a link from my webserver :
http://www.net-createurs.com/wpw/ie4_9x.zip
Hope it will help (those '90 Mac users, finally, I like their way of life).
JP