I am having similar errors with the Media Library. I upload to a post and get an error that the upload failed. However when I go to the Media Library it is there and attached to the page/post. But I cannot access or view the library from the page/post so that I can insert it on the page/post.
I’ve tried reinstalling WP, the theme and turning off JetPack plugin. This is a serious pain in the butt. It was not resolved with the new WP 3.5.1. Work on a client project is now dead in its tracks until this is resolved. It is obviously connected to a WP update as I was able to do all of this before without an issue.
Please HELP!!