Can't deselect "Limit selection to visible"

First of all: Hi to everybody!
I used Blender about a year ago and now I’m trying it again. I have a problem with the “Limit selection to visible button”: I can watch it but when click it, it doesn’t work in any way, the button doesn’t look like it was pressed and the selection keeps limited. When I used Blender a few years ago, it worked in the same computer.
It’s probably a stupid problem, but I’m not able to sove it.

Forget it, the problem has dissapeared autamatically.