Hmmph. Win98 systems. Intellipoint software installed on each. KB891711 patches applied. Some systems stay fine, some cough up BSODs, some glitch the mouse operation, some just hang... it gives new meaning to "your mileage may vary." And so much for the theory of the absolute repeatability of digital technology.
Since 98 is no longer "officially" supported the patch probably wasn't very thoroughly tested -- Because Goldengamegod won't fit:p