Some attachments don't get displayed after upgrading

Hello.

I’ve written a plugin that basically allows people to post their own YouTube videos. As a post thumbnail, plugin was supposed to get the YouTube video thumbnail, put it on the server, register it into wordpress as an attachment, and then set the attachment as post’s thumbnail. And it worked like a charm, but in version 3.3.2.

After upgrading to 3.4 some weird things started to happen. For some reason, WordPress refuses to display these “downloaded” attachments. They are on the server in the correct directory, the URL of file is fine. They used to work in the previous version. I can go to “Media” page of admin panel, edit these images (where they get displayed correctly, I can rotate and stuff) though they won’t save.

Here’s how it looks in the admin panel (green – working attachments, red – not working ones, from submitted YouTube vids)

I have set up a clean wordpress install, here are the “live” examples of attachments:

Not working one – http://gct.lh.pl/wordpress/?attachment_id=23 (that link next to publish date – 480 × 360 – will take you straight to the image file on the server)

Working one – http://gct.lh.pl/wordpress/?attachment_id=17 this one was uploaded in old-fashioned style, using wp_handle_upload (the plugin also allows to upload images and that is working fine).

Here’s the code that I use to download YouTube thumbnail and save it as an attachment – http://wklej.to/J9gHL/html . I’d like to note, that CHMODs are fine, 644, as all the attachments.

And here’s how these attachments “look” in the database – http://dl.dropbox.com/u/40331962/posts.txt first one doesn’t work, second one is the working one.

I appropriate any help, I’m out of ideas what’s wrong.