How about a problem when u holding the slider bar to scroll-down or scroll-up, in Firefox it loading data faster than IE (i'm using IE7)? I don't know why.
What do you mean with "loading data faster"? The loading of the cells, or the loading of the snapshot or maybe the movement of the slider?
I don't know if it could be related to JS code rather then on the IE's engine.

And it still has 100% CPU when you first load the page.
How much time does it stand on 100%?
You should try to cut down your page until you find what's so heavy on the cpu. Note that a lot of data rendering and illumination could be heavy.