Content unavailable to anonymous visitors. in spite of correct permissions

I'm having a devil of a time trying to figure this problem out. At first I thought it was Views, but now I don't think so.

What first happened was a block created by a view would show the wrong content type - one that was not supposed to be visible in the view - for anonymous site visitors only. When I was logged in, I saw the correct content.

At the same time, a user wrote a blog, that was only visible when logged in. The rest of the items in that view were visible to anonymous site visitors, but the newest entry was not, either in the view or the actual node itself. I reverted to saved database of the site and it was ok.

Things seemed fine - until a user added a blog and *poof* same problem. This time I reverted the database again - except when I edited some content, the problem with the wrong content type in the view reappeared.

I tried clearing the Views cache. I noticed when trying to edit a view that I got a page with just 3 'switch to plain text' links, and firsted updated Jquery Update (copying the misc folder to make sure it was up to date) and then just turning off TinyMCE.

I'm in the process - prior to these issues appearing - of working on a copy of the site to upgrade to D6. I've asked a couple of users to try to write some blogs and see if they have any issues there. I'm not sure what it is at all. Any clues? Thanks.