[Greasemonkey] delay rendering while changing css-display mode of divs

[Chris Hayes]

This question is not GM related but i hope to find some JS experts here.

I have a page with a menu with 4000 items. Every item is a DIV on its own.
I need to hide or show all divs according to arrays, i do this by 
setting the css display to block or none.
This takes a while and I was wondering whether this might be caused by 
the browser re-rendering the page 4000 times.

If this is true, is there a browser-safe way (at least FF1 and IE6) to 
temporarily stop the rendering until I'm done?

The page contains a lot of content that is put in usnig xml_request.

Chris