I just upgraded to 3.4 and uploaded my first image after the upgrade. The image shows up in my media files, but the title shows, as opposed to a thumbnail of the image as before. However, sometimes the image will show up, sometimes not. Other images, which previously showed up as a thumbnail, now show us as title only, too.
I received the following email from WP after the upgrade: WP Super Cache was removed from your blog but the mod_rewrite rules in your .htaccess were not. I assumed this was because I disabled all plugins prior to the upgrade. But, then I enabled them again so I am not certain this advisory from WP is the problem, or not.
The site displays fine, it's just that I want thumbnail images to show up in the media library, not the title!