http://blog.drittbra.net/raspberry-pi-xbmc-video-calibration/

One of the things that really irritated me lately is video calibration on XBMC. Everytime I restarted the Pi I had to adjust the video settings although I had set the values previously, it didn’t save them correctly or it is perhaps not meant to be stored at all?. Again after searching the web i found a lot of stuff but nothing that really helped, some talking about a frodo patch, others about changing some file on the system (without saying anything about a path to the file), and some long forum treads about people having the same issue but no comments on how to fix it, then I came across some guy talking about adjusting the skin size, and this seems to be a working solution!
§ Video calibration workaround that only works until you reboot: open menu “system” > “settings” > “system” > “video output” > “video calibration” and then adjusting the image manually to fit the screen
§ Skin size workaround: open menu “system” > “settings” > “appearance” > “skin” and edit the “zoom” value to “-6%”

Did a restart and it was in perfect fit with my TV screen, worked ever since [:)]