Footer rises above bottom of Left Column Navigation Module

Its ok in opera, Firefox and Chrome, but in IE 7 my Footer rises above bottom of the Left Column Navigation Module (obscuring it) when the content in the main column doesn't reach down the page as far as the Navigation menu does.
Anyone know why, or a workaround?

Just in case anyone else runs into this, my navigation module in the left column had absolute postioning, and this seemed to be the cause.