One thing you might want to try is putting your ATA ahead of the router for testing purposes. If the breaking up goes away, then it is something in your router. I am not familiar with the OBI110 but I would suspect they are not up to Grandstream capabilities. Any weakness in you system will appear with VOIPo as they don't compress the audio stream (this is a good thing as it gives the best audio quality). You might also ask VOIPo to change you to a different CODEC to one that uses compression (again for testing), there will be a slight degradation in audio quality but it is slight and most people can't detect the difference. Just throwing some ideas out there, I know it can be frustrating. Let us no how it goes.