Okay this is on my son's machine at school (Gateway 600 XP Pro).

Some websites are shutting down on him as soon as he navigates to them, form what I saw at Christmas, it appears to be Secure Sites (https), but there is no rhyme nor reason to it.

It would seem that if a browser had a set security setting, it would shut down all sites that didn;t fit the profile. I am at my wits end on this one.
Thanks in advanace for any help. By the way, scans with AdAware, Spybot, and CW Shreddrer turned up nothing. Machine is fully updated.