I have three Polycom Viewstation systems. Make sure that your microphones are at least 4 feet away from the speakers. Try turning down the speaker volume or reducing the microphone sensitivity. Feedback could also be happening on the remote end so make sure they do the same. Another problem could be the room acoustics. Flat surfaces such as conference tables or windows can cause problems as well. For the conference table raise the microphone a good 2 inches above the table (put it on top of a phone book or something like that). If you have curtains or blinds close them part way. I'm assuming that you have the audio cables connected properly here.