Sub-Menu hot spot area problem

I am not sure when this started but the hot spot for sub menus has changed size. This is not a problem for most of our web site visitors but for those of us with management access right - for whom there is a third level of menus, we cannot click on the third level menu items. You can see the problem though without special access. On www.ccrc.co.uk hover over any menu item e.g. "About CCRC" then the sub menu "Cruiser Racing" and you will see the grey area is wider than the white menu area. This is not a problem until there is a third level menu. Any suggestions on how to fix this, please.