Before getting all detailed about how I do this...
Has anyone heard about a problem where if you click the screen while the swirly gig is showing the page loading via an update panel, that the screen loads with munged looking CSS. As opposed to if you let the swirly gig load on the update panel and you don't touch the screen at all during the process, it loads fine?
Seeing if someone says "This is a known issue, all you have to do is..."
I'm sure I won't be so lucky, but worth a shot.