For each float left, add clear:left, for each float right, add clear: right.
It'd depend on the order of each floated container though. Another option would be to try keeping one set of floats from one column (i.e. the float lefts or float rights) and remove the float property from the others in the other column so they wrap to the side of the floated boxes.
EDIT: a working example: http://cssdesk.com/Xan5j