So, are you saying this could be fixed by simply copying the SpryAssets folder, duplicating it as Spry AssetsVertical and then deleting the parts out that apply to the other menu?
It is not working in Firefox or Chrome under Windows XP for me. See the screenshot attached – it shows Firefox and IE side by side. This is using Firefox 3.6.6 – just downloaded it. Same happens on Safari, both in Mac and Windows XP.