So I just had this happen recently to two blogs that I maintain. The home page of the blog showed up fine, but when I clicked on a link to go to any page other than the home page I would get a 404 not found error. Pretty crappy, but the good thing is it was simple to fix. Log in to your Dashboard, under the Settings tab there is a Permalinks link. Click on that and then click the Save Changes button. This re-creates the .htaccess file and that should fix the problem. I found this solution on WordPress’s forum here. WordPress Rocks!