Hi, I noticed something strange today on my m4v files in the Finder, in the list view. There is no more thumbnails on them, just a blank icon: In icon view all is OK. And even in list view, if I change the size of the icons to the larger one in view options, the thumbnails appears: After some investigations I noticed the same problem with some jpg, or mp4 files. Mp3 with covers seems to be OK. I tried to create a second user on my Mac, as well as logging as a guest, and the problem is not here, so it's definitively linked to my account, and not a issue related to El Capitan, I think. After a lot of readings, I tried several things without success: - delete com.apple.finder.plist - rebuild "display of folder content" with Onyx - fix permissions via Terminal - repair disk - general maintenance with Onyx (deleting caches, etc...) Nothing fixed the issue. Any idea? Thank you in advance.