Do you have both your PC system, Cisco device and your down stream Internet connection (Cable modem etc..) all connected to a common hub? Is the hub a fixed speed device and is all of the connected devices all running at the same speed? You may need a switch Vs a hub which has independent speed sensing ports so you can inter-connect the devices together (if they are running at different speeds).
Also check your cables are the OK are they Cat5 or Cat5e (don't waste your money on Cat6 cables)