Really wierd Firefox issue

[RivaLiva]

This just started happening today when I watch a video using the firefox browser.

When I play a clip on Youtube or http://www.revision3.com/ Revision3 it will play normally. But when my mind wanders and click on another link to view it in a different tab the video will pause.

The issue I have found out is when the video is physically covered(so I can't see it) it will pause. When I scroll down in Youtube to view the comments and the I can't actually see the video anymore it will stop playing and pause, when I scroll back up it will automatically start back up again.

Also when I adjust two firefox browsers on my screen and in one browser play a youtube video and then with the other browser I will drag it over the video. When I completely cover the video it will pause like before and then when I move it back it will play again.

Basically when i can't see the video it won't play the audio.

Anyone else run into anything like this before? It just started today and I didn't install anything recently. Now that I've typed this out though there is an update that i forgot about that I clicked to do it "later", so maybe I will install that and see if it fix the problem.