it should work, it's just that yours doesn't.
if it was my computer i would:
do any system updates and software updates.
repair permissions using applejack.
try the both usb sockets, make sure the camera above the display isn't in use (unlikely i know, but it draws some usb power)
have no other ancillaries plugged in.
check the camera is set to tethered mode (or whatever it's called in the menu, i can't remember)
i would also download a trial of capture1pro to see if it will tether with that.
if that doesn't work put the computer closer to the set and use a 5m cable