This was both the ActiveX version for Internet Explorer (we have IE 8),
and the 'other plugin-based browsers' version for (for us) Firefox (FF4).
Today, on Firefox, we found that:
- YouTube videos wouldn't play - there was just a black rectangle where the video should appear; and
- the Videos available from BBC News (via the 'Latest Headlines' bookmark in the Bookmarks Toolbar) didn't load. The text appeared, but the space where the video frame should appear - the space was null.
On IE there was neither of these problems.
Without going into the several steps of diagnoses, here are the conclusions:
1. IE and Flash 11.3.300.257 'ActiveX' appear to be OK
2. Firefox and Flash 11.3 'for plugins' don't work together. (I can't say they NEVER will work, but they didn't for us.)
3. We rolled back Flash (for plugins) to 184.108.40.206, which we had kept archived. Video functionality was restored.
4. A Google search disclosed other reports also of Firefox (various levels, including up to 13) having the same video problem. There were scattered exhortations to switch to Chrome, which apparently does not have these problems.
5. Final conclusion: 11.3 works for IE, but not for Firefox. 11.2 is necessary (for now) for Firefox.
Reference also the previous Flash article, flash-player-11-2-fixes-vulnerabilities-automatic-update-t17791.php .