This regression bug inhibits the effect of any styles applied to the :hover pseudo class of a nested element (in this case a block level one).
When the element (in these examples, div#main) with :hover styles applied to it is the child of the body element, it results in the expected behaviour (styles which are defined specifically in the :hover state are applied to 'div#main' when any area of the box is hovered over ('content box', any padding values & any border values)).
I have created two test cases each with consistent styling. In each case, I have defined a four pixel border and a 10px padding value to demonstrate the expected behaviour more concisely.
'div#main' behaves as expected if there are at least children nested within it.