Alt key problem with MacBookPro

[Riccardo Romoli <ric.romoli@gmail.com>]

Hi to all,
my name is Riccardo, and I'm a newbie of Debian. Using the Debian-Wiky
I was able to install Debian 6 as single boot on my MacBookPro
(v.3.1). The only problem I notice, till now...., is about the Alt key
that doesn't work. I tried to configure the keyboard with the
graphical interface but I wasn't able solve my problem. If, for
example I press Alt+Tab,  I was able to switch between the different
windows, but the Alt key doesn't work both in the various text editors
(emacs, gedit...) and in the terminal, to type the extra character
such as tilde, square brackets...

How can I solve this problem? Is there a way to manually map the keyboard??

Best
Ricardo