Voice applications failing with Mac


I recently bought yahoo messenger voice to use my computer for incoming calls. When a call is placed to me my computer does not notify me of an incoming call. I worked with Yahoo and everything on their end is fine. To test this, I also bought a skype number with the same problem. When either I call the number or call it through google voice I am not notified. It has to be something with my computer.
Firewalls are down, speakers work just fine in all other applications to include yahoo and skype and google. It is just the receiving calls issue. Once the call goes to voicemail I do receive the notification that I have missed the call and am able to listen to the message.
Please help!