@NoClue: What brand of PCMCIA USB card are you using? What version of Windows? Take a look at this link for some ideas on how to solve USB problems. http://www.usbman.com/WinME USB Guide.htm
Does Windows report that the USB hub has been installed correctly i.e. no exclamation marks in Device Manager etc.? Maybe you need to switch off the onboard USB controller in the Bios?