I have a similar problem as the OP. Everex laptop running Vista Home Premium. In the last couple of months, whenever IE7 decides it doesn't like a webpage (certain ebay pages for instance), IE7 may or may not crash, but in either case I lose my wireless network and I can't reconnect ("windows cannot find any wireless network"). I have to reboot the computer to get my wireless network back. If IE7 doesn't encounter a problem webpage, I can stay connected all day. (IE6 on my XP machine has no problem with the same webpages BTW).

So... as far as I can tell, there's some BUG in Vista re: IE7 and wireless networking.