Preview conversation actually creates the conversation. Has happened twice to me now. I will click on 'preview' when I've finished typing here to see if it does it again.
And I was going to put this in 'site tech stuff' but I thought I'd have a mooch through the threads there to see if it had already been mentioned and every time I click on a thread (the one about pagination for example), I just end up back on the topics page instead of looking at the thread.
IE7, Windows, PC if that helps.