My frame size on play back has suddenly got narrower and I can't change it
I'm relatively recent to final cut pro 10 but I've edited several projects recently, they all automatically went to wide screen and when I exported them, the video filled the entire screen. This week I edited a new project and exported it and now there is a black frame around the video instead of it filling the screen. I then noticed that on my older projects the playback screen on final cut pro filled the entire window in widescreen and then on this new project it didn't, but instead two grey strips on either side made it wide screen.
So now anything that I export does not fill the screen. I can't find anything that helps me change back the settings. I don't even know how it changed in the first place, any suggestions welcome.
MacBook Pro, OS X Mavericks (10.9.2)