It's just that the vBulletin forums have what is called a "liquid design". This means that it will flow to fit the window size. (Go ahead and try it out on the
front page.)
The tables and text all reposition themselves depending on the size of their container element. In the case of the button bar, it 'breaks' the liquid design by forcing itself outside of the original table width.
This doesn't show up on higher resolutions, since the button bar can fit within the window container. On lower resolutions (800 x 600, for example), it becomes glaringly obvious.
Just a suggestion.
