IE6 Shutting down some sites..

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.

May be because of restrictions that are setup on the school's firewall and/or the ISP.

He is on an independent ISP in his apartment.

i have posted the same post here and other forums no help yet, i have certain sites that i go to they will load and then completely turn ie6 off, i can go to www.radioshack.com and several others and as soon as they load if i have 3 or 4 websites open it kills them all, doesnt do it on myie2 or opera. some one else posted a question just like this also sometime back on the security and viruses forum. no one explained it there either