Discount Group not accepting customers

[tonibarcelona]

No, Zencart doesn´t refresh the screen with the users at the group, because doesn´t write at the db!!
Yesterday I enter at database with phpmyadmin, and the table users registers were empty at the groupid.
I wrtote "manually" at db the griup id for several users and after that in Zencart Admin, the users were at Group, and the discount Group worked well, but I still not allowed to put a users at Group throught Zencart. It seems like zencart dosen´t write the db!!

Do you know why?