I've just tried a new download and as soon as it started to open shut the tab for "Welcome to Opera". It works fine now. What a shame that the "Welcome" page that would tell new users all about Opera is the one that hangs! I use Windows XP (service pack 3) and those on the Opera forums reporting problems all seem to be on XP - Vista users don't seem to have the same problem.
Another interesting point is that, although I removed Opera with Revo Uninstaller yesterday, and deleted all the "extra bits" that Revo found, nevertheless when I downloaded a "clean" copy of Opera today it still had all my bookmarks and other information intact so there must have been a little something somewhere on my system that Revo Uninstaller had not found.