Please, forgive my unperfect english

I can not hook a shape to gride or to guidelines.
Indeed, for example: I make a square, if I modify the dimensions, dragging the cursors, the sides of the shape snap to the grid automatically.
But if I want to modify the square for a second time, I cannot catch the sides, or the points, to grid or guidelines automatically.
Practically, I can catch the shape to grid/guidelines automatically only once, then it's no longer possible.
Nevertheless I checked in "property" in menu FIle and setting of coupling is activated.
I use Inkscape 0.48.4 on ubuntu 13.04.
How i can solve this problem?
Thank you!

Bye bye