I am trying to find a SIP client that works on Ubuntu 12.04. I have an account on voipdiscount (www.voipdiscount.com) and 12voip (www.12voip.com) Earlier on Ubuntu 11.10, I was able to use SIP clients: Twinkle, SFL Phone. Using these clients, I was able to access my account and make the phone calls to different destinations. But after I installed 12.04, Twinkle, SFL Phone and Ekiga stopped. Whenever I try to make a phone call using one of these software, for some reason they are not able to register. They are failing. Any suggestions as to what I can do? Is there any SIP client that works on Ubuntu 12.04? Thanks!