caffinated - 2:31 pm on Jul 23, 2012 (gmt 0)
Thanks rainborick - the solution had to be added the css to the inner div. The idea here was to provide acceptable non-js degradation so the HTML5shiv was out of the question in this case. But I am testing in IE8 so you answered that part thanks.
Paul_o_b - I left both height and max-height in the css to illustrate that neither was working - but I now know why thanks. The HTML5boilerplate default css applies display:block to all of the following: article, aside, details, figcaption, figure, footer, header, hgroup, nav, section and I always apply a css reset which applies display:block to divs.