Hi,
www.logitech.com/revolution works fine on my version of Safari (2.0.4 v419.3) so it's not specifically a Safari bug as such.
One quick test you can do to help narrow down things is to try Safari in another user account.This will help us to know whether your problem is local to your account or system wide. If you don't have another account you can use System Preferences -> Accounts -> [+] to create a test one (and [-] to remove it if needed)
For your your internet connections are you using any proxies? (You can check in the System Preferences -> Network pane)
Also, what Safari add-ons have you both added in the past? Maybe we can track it down to a common add-on between you both.
