Can't insert images

All of a sudden I can’t insert images into posts. It was working fine yesterday. I go to insert an image, select my image from the media library or my PC, click insert into post and it inserts the image into my post. However, once I press Update to save, the image disappears. I have tried it in different posts and have tried just typing in the html code for the image. I have also tried different images, de-activating all my plugins, trying different themes, trying a different browser, logging out of wordpress and back in again, rebooting my PC, downloading a new copy of WordPress and copying over the wp-admin and wp-includes folders via ftp into my wordpress folder on my server. Running out of ideas now.