well, i really don't know what happened, i restarted my pc (i use slackware 12.0 with fluxbox) and logged in, i typed "$ startx":

(...)
Fatal server error:
xf86OpenConsole: Cannot open /dev/tty0 (Permission denied).
giving up.
xinit: Connection reset by peer (errno:104): unable to connect to X server.
xinit: No such process (errno:3): Server error.

before showing this it shows other errors but i changed privileges of interested files.

using root i can start the X server, i used init 4 to login with my account.
Once logged i tried to go superuser

$ su
Password:
setgid: Operation not permitted

ls, cd, vim and other applications are running without problems.

Before I rebooted I did a lot of things mmm... installing mplayer with plugins (packages), installing steam with wine, but the most important and decisive (i think) was installing MySql (well, reinstalling, becouse i have installed it from the slack installation) following this guide (i can't post it because this is my first post) "Installing Apache, MySQL, and PHP on Linux" from "Host Library"

i think it's about user privileges, or groups, but how can i fix it?

help me please, sorry for my bad english.
thanks

Have a look in this thread ...
http://www.linuxquestions.org/questi...ssions-296421/

Specifically, go to the site
http://homepages.paradise.net.nz/~cameronk/progs.html

You'll have to edit the script/process since newer versions of slack
use a MANIFEST.bz2 rather than a gz, but you should get the idea ...