I'm Brazilian. I have a problem with my indicator-applet-session. One day the user-name simply disappeared. so I don't know what i do to back a normal state.
I've had indicator applet issues before, but not recently. I usually do this as a test: Right-click on an empty spot on your existing panel and choose 'New Panel' to make a new panel. The main applets I've had to delete and re-add during the course of things were Indicator Applet, Indicator Session Applet, Notifcation Area . If you add all three and they look fine, then you just need to tweak things.
You already know which applet is the problem here (or if you didn't, right-click on the problem indiactor and choose 'about,' and it will tell you). Use
killall gnome-panel && gnome-panel
to restart the panel. Or log out and back in (which if you haven't done since this issue appeared, you should do regardless).
If that doesn't work, log in with a different user and see if it is working normally.
Off the top of my head, this could indicate home directory permission issues, dot-file modifications gone bad, or something wrong with authentication (bad line in /etc/passwd, partial PAM failure or mistmatch). Those can all be tested if you are still having problems.
If you've replaced any default packages that you could recall, that would also be something to consider.