Can’t access certain things in latest wordpress

I just updated to 2.8.4. Everything on the site before the upgrade looks fine, but when I try and add a new page now, the title shows, but there is no content. The page is the length it would be if there was content there, but it’s blank. Also in the editor, I can’t change the HTML editor, and I can’t preview any changes. Any ideas to help me? I have tried deactivating the plugins but that didn’t do anything. Thanks.