[SOLVED] Drop down withing WP custom menus not appearing under hover

Am using Atahualpa 3.5.3 with WordPress 3.0.1 on this site: http://signsnh.org . After creating a menu structure using the WP custom menu feature, the items in the menu bar that have child menus show the double-down arrow, but when you hover the mouse over the parent menu name, the sub-menus do NOT drop down -- so there's no way to navigate to the child pages. This worked fine before I used the WP custom menu tool and just relied on setting up the hierarchy using the attributes in each of the Pages. Is this an Atahualpa issue, or a WP 3.0 issue? I can't find anything on either the wordpress.org forum or this one. Incidentally, am testing with both Firefox and Chrome.