After 10.7.5 update, internet browsers do not work for non-admin user.

My daughter has a Macbook Air running OS 10.7.5. I'm the administrator and have no problems. My daughter has had a separate user account ever since we bought the computer 13 months ago (just out of warranty).

The computer is connected to the internet via WiFi router.

Since the most recent system update, we can't connect to any webpages when logged in under my daughter's user account.

Connections time out and the error message suggests we disable firewalls and proxies (there are none... I think).

She can still connect Mail, Skype and iTunes Store but not Safari or Firefox. We downloaded Google Chrome with the admin account and installed after this problem showed but it has the same problem when using her account.

I've searched the Apple forums and elsewhere and seen a few similar problems but none where the administrator's browsers work and the user doesn't.

By the way, there are NO parental controls activated.

Please help.