I am aware of this issue, but haven't identified the problem yet (not on Mountain Lion with my current device) -- any help from the community would be much appreciated! Post any information that would help to resolve this issue here: https://github.com/groundworkcss/groundwork/issues/12

The tooltips work fine for me on Lion + Safari Version 6.0.2 (7536.26.17).

Still killing Safari -> Versión 6.0.2 (8536.26.17), Mountain Lion 10.8.2

odd - not killing safari here (5.1.2 - snow leopard) - maybe it's a safari 6 thing?