Pages or posts that contain images not updating

Hello

Last week 4 sites on the same server were hacked, the header php code was changed but luckily thats all so they were back online in no time.

I then read up on adding security features to the sites. I changed all the admin names and renamed the all the wp_ prefix’s in myphpadmin.

since then any page or post that i have been trying to update that contains images (only ones with images) redirects to /wp-admin/post.php gives me a 404 error and doesnt update.

I have since crawled the net looking for solutions, have deactivated all plugins, changed the database prefix back to wp_ and everything else that i have found including adding settings to the htaccess, none of this has worked. It has something to do with the fact that there is images on the page or media settings and i cant figure out what. please please help its driving me insane!!