I've installed a virtual machine on my computer so I can test under IE6 as well. So far I haven't been able to duplicate it. I've visited a variety of sites running 7.0.2, not just my test board, and the preview works every time. If the site is slow, there will be a bit of a delay as it has to send the request to the server and then back to the browser, but I haven't seen it actually infinitely hang yet.
