Xbian stopped buffering by itslef

[rikardo1979]

btw, why do you need screen calibration ?
So many eople get confused and always trying to solve simple thing the hardest way. Not saying is your case, but can you tell how you are connected to the TV, what connection, what is the TV (model) you have?
As I never needed to calibrate the screen, and I use XBMC for more than 7 years, I've installed the XBMC for many people on many different setups, and honestly, never needed to calibrate it.
There is an simple thing what most of the people overlook always, and that is the overscan setting in TV. 99% of TV's has this option.
And also 99% of TV's has the aspect ratio for all inputs on TV pre-set to Auto, where this cause the trouble to picture reproducing from external sources.
So my recommendation, not just for you but for all is to start from there and not to go and calibrate the screen in XBMC settings. This option should be as the last to do.

So
-check the aspect ratio on the TV for RPi input (make sure you have no Auto mode but forced 16:9)
-check the 16:9 overscan (make sure is OFF for RPi input in your TV settings)