I have two laptops running Debian stable 7.3 and Ubuntu 12.04. I installed Jitsi 2.4 build 4997 on both.
They both have integrated microphone, one has built-in webcam and the other has aUSB webcam.
While the video works, i can hear nothing both sides. I checked the volume and the toggles. The microphones do work. I use Jitsi default configuration.
I can provide additional informations as needed. I am attaching the log .zip file in case it is useful.
firstname.lastname@example.org (200 KB)