With the plugin activated, the video thumbnail does not show, only the name of the file, which is unplayable. (EDIT - Audios also)
Disabling the plugin brings everything back to normal.
Now, this one has me stumped. It doesn't appear to interact with thumbnails at all... Maybe it's that before they were cached and they're not working for an entirely different reason? Can you try disabling the plugin and see if it fixes it?
Ok! I had it disabled since yesterday. I've just enabled it, and i'm able to upload videos. Sorry for the noise, maybe it was another plugin (i disabled most of them to solve this). I'll try to find the guilty one :)