voip usb phone

[Metro]

I have recently bought two different types of usb phone for use on skype. I have also had a Actiontec chatterbox which works well but was looking for better integration with the skype program. Both the usb phones suffer from horrendous interference on sent audio from the microphone, the received audio on the speaker is fine. Are both phones (one is a US Robotics 9600, the other a generic desk phone) faulty or can I cure this interference by adjusting the settings?

Windows XP, Amd athlon 64 3000+, 1GB Ram, 200 Gb HDD on 2mb adsl through BT voyager wireless router!

Many thanks