Background-image doesn't appear in #main in twentyten.

I’ve tried everything I can think of, but I cannot get a background image to repeat in the “div #main” of my twentyten _child theme. I have tried both absolute and relative paths to the image file within the twentyten _child theme.
My current css looks like this:

div #main {
    background-image: uri ("images/paper_bg.png");
    background_repeat: repeat;
    }

but I also tried adding the background declaration to

#main {
    clear: both;
    overflow: hidden;
    padding: 40px 0 0;
}

with no success.

There is another curious thing: my code shows up in the them editor and it is the same code that is in my child folder. But in Firebug it looks like this:

div #main {
       }

No declaration!

Background-color works as expected.

Can anyone give some insight on this problem. I would appreciate it.