Topic list width - not using full width, what gives?

[omega]

I've borked something in the custom CSS - lists of topics, popular, recent etc. etc. are NOT using the full width available - say 75-80% of the width available is being used - I have unused space to the right size of the recent post preview. - it's lie there is a blank column.

The primary nav menu fixed at the top is fine, this is what I am comparing it to.

Any idea what is the controlling element here in the CSS?

Could a conflict somewhere too but I'll look at this later... when I turn off the custom CSS to see if it reverts.