Hello Paulo Teixeira,

I've suffer a lot with this problem too, but finally I found the solution.
I think you speak portuguese, but I'll write in english cause this post may help another peoples around the world.

Edit the file /etc/environment and leave it like this:
Code:
LC_ALL=pt_BR
LANG=pt_BR
LANGUAGE=pt_BR
LC_MESSAGES=pt_BR
Reboot your machine and try.
Post here your results.

Samer Eberlin.