canvas has gone black

Hello,

I was wandering if anyoen could help me. I have just been editing (in FCP 7) then suddenly the canvas window has gone black and I am unable to view anything in it. If i try playing the timeline, I can hear the audio playing but nothing in the canvas.

Double clicking a clip in the timeline, I can see/play it in the viewer. I have re-started my computer, and the same problem. I then opened up other projects with the same outcome. Trashed my preferences, re-started and no luck.

Any ideas? Thank you in advance