Check to see if there is a border or margin given for the Page Background on your CSS page. If that fails, check to see if there is anything in your header template that might cause a gap - table code, page breaks, borders, etc...
It's hard to say for sure without seeing your style admin, but those are good places to start.
Thanks, I'll check the CSS thing.
The weird thing is the logo on the left side goes all the way down and touches the next table...hmm.