IE 5.1 illegal op message and screen jitter

WIN98SE , IE 5.1
Stable system. Earlier today I got 2 illegal operations messages while visiting yahoo search sites.

Shut down and used my Configsafe restore utility to restablize.
Hours later, all seems fine until I got a site that was loading improperly, started jumping around.

SO I immediately tried to exit, couldn't close. Finally shut down, using contaltdel.
When I rebooted, I was going to restore my system to before the problem
Configsafe got stuck and started wobbling. Tried system file checker. No problems found.

I rebooted to safe mode, restored to earlier. Rebooted and the problem was still there. I went through TWO IE repair cycles.
The second time, the screen seemed okay.

Norton does not see a virus. Any one know what could be happening? The only recent system operation done was a defrag yesterday.
Could I have picked up a virus on the bad site? Or is it possible that a faulty website actually caused this much trouble.

 

It could be the script at the site.

The text of your illegal operation errors would help, though.

Next time you get one, hit the Details button, and tell us what it says there.