Suite Installed Suite, worked fine but now for some it doesnt
 

Hello,
I upgraded my live site from 3.8 to 4.0.2, worked great on test sites etc. However for some reason now it appears it doesn't work for users using IE7 or lower, though sometimes it will work (mainly if they've never been to the site before)... I am thinking it is just cookies or the cache; I'm at work and can't really test (work blocks me from deleting my cache/cookies...). Could there be another issue I am not thinking of?