OGG videos with extension ogv don't thumbnail, see e.g. [[Wikipedia:Featured picture candidates/Propaganda of the Spanish American War]]. The search http://en.wikipedia.org/w/index.php?title=Special%3ASearch&ns6=1&search=.ogv&fulltext=Advanced+search might shed some light on the problem. Possibly similar to bug 14524.

Sample files:

*[[:Image:Shooting Captured Insurgents - Spanish-American War.ogv]]
*[[:Image:Wikipedia - Mitchazenia video.ogv]]

Version: unspecified
Severity: normal
URL: http://en.wikipedia.org/w/index.php?title=Special%3ASearch&ns6=1&search=.ogv&fulltext=Advanced+search