I just noticed this same issue w/ the general settings page of s2member plugin. current wp/mac/chrome. I will probably fix it myself but i wanted to let you know.
edit: s2member has a z-index of 100 on the div class ws-menu-page-group-header the flyouts appear to be z-index 1000 so idk what the issue is, but when i set the ws-menu-page-group-header to z-index 1 in chromes property inspector it works as expected.