My tech specifications: Ubuntu 10.04, stripped down with an Openbox WM. Dell, with integrated webcam and audio.
Google Voice/Chat/Video/Hangouts all stopped working for me. Other video – Skype, for example – worked just fine. No idea what happened, or even particularly when it happened, since I don’t use the service all the time. Happened no matter what browser I was using, no matter where, what firewalls (or lack thereof) were up….
The plugin would install (because I stripped it out and put it back in half-a-dozen times) and there’d be a black square with no video or sound when I went to verify my settings.
Turns out it wasn’t me. (Note: If it’s working, don’t “fix” it!)
It’s a known problem with version 3.10 (which is “current” as of this writing) of the plugin. After finally stumbling across this thread I found the download links for version 3.7.
EDIT 7 Feb 2013: The above download links no longer work. There is a copy of each deb (both 32 and 64 bit) at https://www.box.com/s/yn3ht0925yvxqslqp4h8
I uninstalled 3.10, then downloaded the .deb package, installed it, and BOOM. Good to go again.