Comment # 10 on bug 1041794 from Andreas Stieger

(In reply to James Knott from comment #8)
> Also, this occurs on my desktop computer and ThinkPad, in addition to the
> VirtualBox VM.  I dont't think there's NVidia hardware anywhere.

Comment #7 noted the possibility if an incorrect inication of H264 support,
while this would only actually work on NVidia.

> What update happened recently that might have caused this?  If I knew, I'd
> be able to back it out.  As I mentioned, it happened about 2 - 3 weeks ago.

See comment #2 where this is explained in great detail.