I am trying to edit a pre-existing Page (not post) on my blog. I made some changes, then clicked Update Page. Instead of telling me changes were saved, I get taken to the 404 page of my blog. When I create a new page, I can add and save drafts until I get to about 450 words, then I start getting the 404 again. I also notice that the bar that tells me the word count is frozen on Saving Draft . . . I suspect something is going wrong with the Autosave feature.
I installed the WordPress System Health plugin and it tells me about 75% of the rows in my database are revisions. It has highlighted this in red, so I don't think this is normal. There are only 16 posts. 164 rows in the table are revision.
I already tried doing a clean install of WordPress. (I am using 2.8.4.) It didn't change a thing. Can anyone suggest other things to check?