Using linphone/gphone

Hi,
I tried to use linphone,gphone and speakfreely on my machine, but it doesn't work properly, I get full noise. My machine configuration is : VIA GA6VMM m/b, Via chipset. I can use Yahoo! Voice messenger very well on this m/c(on windows,I have dual boot). What could be the problem? I tried using all the three, linphone,gphone and speakfreely on another m/c, Intel SR440X m/b, Intel Chipset, Ensoniq ES1371-AudioPCI'97 sound card, and all three work well. Any suggestions as to what's wrong, and what I can do to get it working?
All help is appreciated very much.Thanks in advance.
Rgds,
Sujita