I've looked through archived posts and have missed any relevant ones to my particular problem.
I had a number of posts created, which have been working fine (viewable, no problems)...went back to work on the site this morning (about a week since I last worked on it) and am now getting the WP 404 error page whenever I try to view ANY of my categories and posts.
The Pages I created are working fine, but nothing else is. I remember trying to create my own category templates, and they were uploaded but I don't believe they were in use. I removed them and am looking through my notes to see what else I might have done, but anyone had this problem before?