Everything pretty much the same here, but I didnt have any problems before.
On Vista with IE 9 it works perfect. On XP with IE 8 it takes a long time to load each page on a thread.
Can you install IE9 on an XP machine? I didn't think you could....
UPDATE: Just checked, no you can't....and therein may lie the problem...
Well you may have answered your own problem.... Can you get IE9 on the machine OR just make sure the same plugins are installed..