Voice communications problem.

Hi.I have just discovered FSX multiplayer and started to learn how to be a tower.When i play as a pilot on other servers, i can hear the tower and other aircraft just fine. When others talk with me (tower) on my box, there are lots of problems:If i use 1.2-2.4K then i get no quality and it is impossible to hear what people say and they have to use the chat. If i use 3.6 or 128K then i get broken up sound and i have to guess what they are saying.I am using the internal sound card that came with my new box (A 3200+ Athlon64/1GB with only 1 year on its neck) and previously i have used other voice communications software (Teamspeak) with the firewall i use without any problems. I have a 10 MBPS connection and it usually allow more speed than that @ 04:00 in the mornings.Anyone have any ideas?