I just discovered that after upgrading to Utopic a few days ago, youtube html5 and flash videos simply don't play in Chrome, Chromium, or FireFox. Videos will load, appear to buffer, but not play at all. The player interface will be responsive, but the video does not play, the seek bar does not move, and no sound is heard. I checked the software updater tool to see if there have been further releases of any of these packages, and it says my computer's software is up to date. I did some searching and found this bug, recently closed from inactivity which appears to describe the same symptoms as I'm having: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1386931
ProblemType: Bug
DistroRelease: Ubuntu 14.10
Package: chromium-browser 39.0.2171.65-0ubuntu0.14.10.1.1106
ProcVersionSignature: Ubuntu 3.16.0-28.38-generic 3.16.7-ckt1
Uname: Linux 3.16.0-28-generic x86_64
ApportVersion: 2.14.7-0ubuntu8
Architecture: amd64
CurrentDesktop: Unity
Date: Mon Jan 5 00:05:00 2015
EcryptfsInUse: Yes
InstallationDate: Installed on 2014-03-27 (283 days ago)
InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016.1)
SourcePackage: chromium-browser
UpgradeStatus: Upgraded to utopic on 2014-12-27 (8 days ago)
modified.conffile..etc.default.chromium.browser: [deleted]
mtime.conffile..etc.chromium.browser.default: 2014-12-27T14:52:55.129179
Going through my browser history, I realized I had definitely managed to play some youtube videos after the upgrade to Utopic, in at least two of the mentioned browsers. I closed everything down, rebooted, and have been able to play videos in all three browsers. I have no idea why all three wouldn't play videos, whether html5 or flash, all at the same time, but rebooting cleared it up just fine. I should have done so before filing the report.