a black thumb in FF
Seen in FF and Safari, in production, test2wiki, and beta labs.
Upload an OGV file to Commons using UploadWizard.
The steps for Upload/Release Rights/Describe should all show a thumb of the OGV video.
In FF the thumb is black.
Safari displays a page icon and ultimately says "The upload succeeded but the server could not get a preview thumbnail".
Thumbs almost always display correctly in Chrome/Chromium, but may occasionally show as black.
IE status is unknown.