Can anyone spot what is wrong with this snippet of CSS?

Works fine in IE but not in Firefox – argh!! The background image (maincolumn.gif) won’t repeat vertical down the column in Firefox yet it works fine in IE.

.rigid-demo { margin: 0 auto; text-align: left; width: 790px; background: url(../images/maincolumn.gif) repeat-y; }

P.S. This is NOT a reason NOT to use Firefox! It’s my shoddy coding that’s to blame, and lack of l33t CSS skills, or however the kids are saying it these days.

UPDATE: OH ARSE. Still can’t get it to work. Sample page here, CSS here, background image here.

The CSS file validates OK.

Why oh why oh why… Works fine in IE, no background image in Firefox. Chuff chuff chuff.