The system has:
RedHat 8.0
1.7 GHz Athlon Duron
SiS 7018 PCI Audio (inlaid in the motherboard)

I already tried by simply enabling the full duplex in Control Center of KDE, however, I noticed that the CPU activity skyrocketed until eventually I received a pop-up window advising: "CPU overloaded. Aborting."

It seems that the full duplex feature is necessary to have Gnomemeeting fully capable or receive and transmit audio at the same time...

Is there any special driver required for that task?

I appreciate any help...

The best thing is to see if your soundcard is supported by ALSA (advanced linux sound architecture) at http://www.alsa-project.org/ it can be difficult to install because the documentation isn't fantastic (its no better once its installed either, i can't find anywhere that tells me what all the options in the sound mixer mean :()

Excellent! It worked great with Alsa! Thank you!