Why Can't I Unwrap?

I tried to unwrapped the bar but there was nothing showing up in the UV Editor. I have tried to create a new mesh and unwrapped and it still did work.

However when I tried it in a new file and it worked fine. This is frustrating.

Attached is the blend file I am working at. Any solutions guys?

http://pasteall.org/blend/13026

Your uv/image editor window is set to show the render result. Remove this by pressing the X button. Then unwrap.

Richard, thank you so much for your help. I got it working. Thanks again.