Ubuntu 12.04, gnome classic, problem with the sudo list

[Uwe Brauer]

Hello

I just installed Ubuntu 12.04 and the gnome-classic desktop.
However when I use the system administration tools to add a
user, who should be in the user list, the user is added but
he is not in the user list.
Did somebody have had a similar experience?
Is this a bug?


Thanks 

Uwe Brauer