"About" widget not working

Dear all,

The “About” widget seem to have a ramdom behavior. I have placed it on the side aera and assigned the page “About” to it.
However when navigating thorugh the site the text displayed changes depending on the section using the text for the entry on that section.

Example:
http://algomasquekilos.es/category/opiniones-de-peso/
Here you can see a Lorem Ipsum text on the widget

http://algomasquekilos.es/punto-de-partida/
Here it is the text of the entry.

http://algomasquekilos.es/sobre-nosotros/
Just here is showing the right text

Could any body help me?

Thanks in advaced.

A.