I suspect your linphone problem has to do with the settings, especially the codec settings. However, diamondcard tells me it is a bit buggy, so who knows. I think ekiga has video so tried that a lot, but the sound quality was not good, probably because I didn't get the codecs right. I don't know why, but twinkle worked great out of the box....the sound is better than a telephone. Far better. I don't really miss the video, but if any of these (linphone, twinkle or ekiga) are going to compete effectively with skype, they will need easier setup and video.