BuddyPress.org

You need to assign a width to your content or muck around with floating your sidebar the way the bp-default theme does it.

Look at the styling for div#content .padder and #sidebar in the bp-default theme’s default.css. That should help you float your sidebar back into the right place.

Or just load firebug on the testbp.org website and see how it’s floating #sidebar into place by changing the margin of the #content .padder.