CSS differences in menu items with and without children

I have a menu bar, and when I rollover the menu text for items with children, the CSS for the other menu items that don't have children changes. All the menu items are bold at the beginning, but after rolling over the parent menu item, all the menu items w/o children, and also some other links on the page change to a non bold or lesser font-weight state.

This happens in Mac Firefox and Camino. Safari is OK.