I`m not sure but this ethernet thing would probably involve a second PC that is closer to the cam and that is forwarding the image it gets from the cam to the "real" destination via some VNC like tool.
You can`t extend USB unlimited useing repeaters, but useing USB-Hubs with an own powersupply should work.
But where is the point why not take a good oldfashioned videocamera and feed the TV-card with it useing an F-BAS or SVHS cable.
