I have a strange problem whilst trying to build a stacked column chart using Highcharts

When the chart renders, the columns don't display, until, you resize the browser in anyway, causing the chart to redraw. (I think)!
The rest of the chart displays (axis, titles, etc) but not the columns themselves.

I get the same behaviour in IE, Firefox and chrome.

I have put my code on jsfiddle - http://jsfiddle.net/gd7bB/173/
Load it up and you should see no data, resize the browser window and tada, the data appears (rather the columns appear)!

Any help on this one would be massively appreciated.