Screensaver ruins fullscreen YouTube videos

Hi, new user here. The problem is that whenever the screensaver activates while I'm watching a YouTube video, I can get out of it (the screensaver, that is), but I never get the video back, only a gray screen. The audio works fine, though. At this point I can hear the video playing, but I am unable to control it and I can't minimize it or do anything else to it, for that matter, except kill it via System Monitor. Other than turning the screensaver off completely, is there any way to fix this, so I can at least get the video and the YouTube GUI back? I'm using Firefox 4.0.1 and the flash plugin supplied in the Software Management app.