A few people have written in to say that the Google Voice and Video software has caused webcam support in Flash Player 10.1 to stop working on Mac OS X.
We recently discussed this problem with Adobe, and they have confirmed it is a bug in the 10.1 version of Flash Player (see Adobe's bug tracker at https://bugs.adobe.com/jira/browse/FP-5730). It affects not just Google Voice and Video, but any application that installs its own QuickTime component.
Fortunately, Adobe has come up with a fix for this in the upcoming 10.2 release of Flash Player. If you have been affected by this issue, you can get the 10.2 RC build that has been confirmed to resolve the problem at http://labs.adobe.com/downloads/flashplayer10.html.
Update (2/8/2011): Fixed the Flash Player download URL.