How many ports on your computer have you -- more than one ? When I initially was going through this, I found TunECU was talking to only one of the ports, and only when the cable was connected to that port, would the communication across the bus begin.
Are you sure you have the correct cables (two - one is the LonElec cable with the OBDII connector on one end and a USB 2.0 connector on the other end, and the second cable is an interface between the USB and whatever connection you are using on your computer.
Has it ever worked in this configuration, or is this for the first time ?