When I hit the preview buton while in draft mode creating a post it goes to a page that reads as follows:
Error 404 - Page Not Found
We couldn't find the page you were looking for. Please return to the home page
I notice that there are quite a few forum descussions on this topic. I switched to WP 3.4.1 back in September (about 3 months ago) and have had no such problem until just about 2 days ago. I am not using custom permalinks but rather leaving the default permalinks as they are. As far as I can tell I have not changed anything yet the preview has quick working.