Are you scrolling with a wheel? I only ask this because mine use to lock up when I would scroll with the wheel. (It would lock up in I.E. other times also, but almost always was when I would use the scroll wheel).
My solution (don't ask how I came up with this, I was desperate and trying everything), but turning my AGP 4x in bios to 2x stopped it completely. I had a Hercules geforce 2 MX and an Abit KT7A, 4x would run just fine until I got into I.E. and was scrolling around and then lockup.
I would suggest playing with some of the timings on your mobo (memory, agp, etc.)
Good luck