I used to be able to prior to safari 5/10.6.4 - but seem to be having issues now.
Can someone please try loading the page in Safari (on the Mac) and see how long it takes to load?
https://wces01.wgpcollege.school.nz and https://webmail.wgpcollege.school.nz
EDIT: Oh, an can you try clicking the padlock in the top right hand corner and see if that freezes safari?
Then, can you load up https://www.bnz.co.nz, perform the above steps, and tell me if there is any difference.
my guess is that the schools SSL certificate is bust, but I'm trying to confirm before I bug the crap out of them to fix it.
Safari is the only web browser effected - firefox works fine, and IE works fine on Windows.