[kube]

It appears from that screenshot it is a 100% layout yet you have a horizontal scrollbar at the bottom. So it looks to be where the border has over exceeded the main table's width and gone down past the left column (as it is the last/lowest item on the page).

Without looking at the code it could be a combination of things from a mixture of pixels/percents or a mixture of margins/paddings/borders. IE is most likely to be upset by margins but you never know with IE.