I recently spotted that this has been happening for some months now, so predates the move to 3.4 although it's definitely not fixed with the new release.
Every image I'm adding to WordPress is creating additional, unwanted copies which appear in my media library. Even if I re-use an image that's already *in* the library, another copy is made and attached to the new blog post. At a quick glance, I have around 50+ copies of one image in particular (a little film strip logo I use for movie reviews).
I've tried erasing the new ones, but unless I then go to the post and manually change it to point at the original I end up with a broken link to the image.
Why is this happening, and more importantly, can I stop it?