That happens from time to time, but it's kind of odd to have it happen on three of the same user's computers simultaneously. That leads me to wonder if some security software you're using is preventing the update from registering.
In any case, turning off any realtime virus / spyware protection and reinstalling IE7 usually solves the issue.
If you try to reinstall IE7 and you get an error message stating that it's already installed, post again. There's a registry hack that'll fix that problem, but I'll have to look it up because I haven't used it recently.
Rich