Echo Cancellation Not working on Optiplex 3040 Micro

Hi 

We are trying to get a video conferencing solution working on the OptiPlex 3040 Micro, but always get echo on the audio. We have tried updating to the latest audio drivers for the 3040, but that has made no difference.

We have tried the system on a 9020 and with the RealTek drivers (R2.79) for that  you get the option for echo cancellation. When it is switched on it works really well. If we try those drivers, both machines are using the ALC3234) the microphone is disabled completely on the 3040.

And help/suggestions would be really appreciated

Frank