Problem with post preview

OK, everything was working fine in WP and then, all of a sudden, I can’t access my Write, Edit, and Categories pages in WP Dashboard. Links, Presentation… all other tabs I can access, but not the ones I mentioned above. It’s like the ones with a preview of the post, those pages don’t work. So now, I can’t write any posts and I can’t edit any. Everything else including my site, works fine. Help!