weird, can't see media in canvas

Hi,
My media is not playing in the timeline (the audio plays). but plays in the viewer (both audio and video ??
To be more exact, I loaded in media from a sony Z5 and a sony pd 170.
the z 5 video track is not playing back (the cursor moves and I hear the audio?
The visible button is on. and the pd 170 media is fine.
Thanks for your help.
Mitchell

Check that you haven't got it set to 'wireframe' in the canvas, instead of 'image' or 'image and wireframe'. It's in the small drop down menu that looks like a broken box at the top middle right of the canvas.