Been poking around and still not sure of the precise problem(s) with these cards and Macs. Some of my search results talked about signal timing issues. Some DOS-USB hackers mentioned Via was the only one who paid to license UHCI from Intel, while NEC etc. used OHCI. Maybe OHCI plays better in older Macs? Maybe needs an additional driver? Found Via has some here for OS 10.2-10.4 (guess 10.5+ is already completely USB2.0-ified), but don't know if they make a difference.