Flash Videos won't stay Full-Screen in dual-monitor configuration.

I'm running the latest version of Flash in the latest version of Firefox on Windows 7 64-bit. I have no problem changing Flash content to Full-Screen. However, the instant I click on my other monitor, it reverts the video to normal size. A few years ago I was able to fix this by using a Hex Editor on the Flash dll file, but I can't find any information regarding recent versions (and old fixes didn't work). Is this a returned bug in the current version? Is there a workaround?