Locked tracks on the Premiere timeline take a noticeably longer time to redraw than unlocked tracks when you zoom in and out of the timeline.
Can you define "Noticeably"? Have you considered that only the CS4 machine is running Vista Ultimate? Have you considered drivers, services, display settings, background processes and the like as a possible explanation?
7 different computers with different operating systems, drivers, settings and hardware - the problem is.
in the video - demonstrating problem
I have not seen that in 2.0, CS3 or CS4, used on three different machines. My redraw is very, very slightly slower in CS4, but nothing near as drastic as your video shows.
With multiple, hi-def video tracks and matching stereo audio tracks, locking all but one or two will slow down redraw significantly if they are expanded and showing thumbnails. Easiest thing to do is to compress them before locking them (the little triangle > on each track). They are then only slightly slower.