I have skype 22.214.171.124 (32bits) installed in my system xubuntu(amd64), my problem is when I recievied a video call and set to full screen mode the video doesn't fill all the screen, only verticaly and I have 2 black side bars, one on the left and one right side. Is there any setting that I can try to get a really full screen? I recievied a video call with ratio of 640x480 (i have checked the technical informations during a call) and my screen resolution is 1366x768(16:9) my video card is intelgraphics incorporated, thanks for now Vladi.UPDATE: Today I recieved a video call from skype and I picked up from skype installed on windows 7 in my machine running Virtual Box, strange the same machine which I have xubuntu (linux) (host), and the call in fullscreen mode was perfect with no stripes on the sides!!! I think there is some configuration on skype for linux that I can achieve the same fullscreen mode that was in windows guest machine.
The reason the black bars are present is that the original video being sent by the other person's camera is in a 4:3 aspect ratio (you mentioned it was 640x480), while you said your screen is 1366x768 which as you mentioned is a 16:9 aspect ratio.
If the Skype application took it upon itself to stretch the image, rather than using the black bars to present the original aspect, you'd see something like this: