gnome-panel stops automatically hiding itself if trisquel menu is clicked again before appearing for the first time

I can't reproduce this bug. Can you update your Trisquel 6.0 installation and see if the problem persists ?

It is updated. Though I didn't try it in a computer with 100% graphic support (Intel instead of nVidia). Will do it tomorrow. (edit, 07 jan 2013: I tried it, and the same happens there.)

P. S. It also happens with alt+F1 instead of right_mouse_button.

P. P. S. At the first time of the command (either right_mouse_button over the menu or alt+F1) after login, there is a lot of HDD activity; I do separate the partitions:

$ df -h
Sist. Arq.            Tam. Usado Disp. Uso% Montado em
/dev/sdb6             504M  281M  198M  59% /
udev                  929M  4,0K  929M   1% /dev
tmpfs                 940M   28K  940M   1% /tmp
tmpfs                 376M  1,2M  375M   1% /run
none                  5,0M     0  5,0M   0% /run/lock
none                  940M  2,4M  938M   1% /run/shm
/dev/sdb4             2,0G  1,4G  660M  68% /var
/dev/sdb1             904G  786G   73G  92% /home
/dev/sdb8              60M   31M   27M  54% /boot
/dev/sdb5             6,9G  6,2G  428M  94% /usr
/dev/sdb2            1007M   18M  939M   2% /srv
/dev/sdb3            1008M   34M  924M   4% /opt

Perhaps trying in a slow machine (or in a Virtual Machine whose performance you could tune by changing the computer resources it is allowed to consume) would allow someone to check this out.