It seems to be related to the number of line segments being drawn on the map. I did not know that this was becoming a problem for IE. I modified the page so that it uses the very latest map control. This helps some but it is still sluggish. With Firefox I can get the page to display in about 4 seconds. In IE it takes just over 20 seconds. With the old control it was taking over 30 seconds with IE.
I guess I'll have to think about breaking the map up. I was hoping that I wouldn't have to do that but I'm not sure if there is any other solution. Maybe I should break it up by division.