Hi,
I think I fu**** up something... I changed the permission on the /lib/ folder so that my user can access it. I did a "chmod 666 /lib" and then yeah it dind't worked... so I tried to go in the terminal again, and when I tried to run it, it told me "Permission Denied!" So, every programs that I try to run tell me that...

What have I did? Someone can help me?

What you did was set the permissions so "root" did not have write (edit: execute -- see spooon below) permission to /lib. How can you recover? I'd try booting from you install media using the linux rescue option, and changing the directory permissions back to their standard settings.

In any case, you should not have needed to change the permissions, since the default is to give everyone execute access to /lib. If, for some strange reason, they need "read" as well, try 771 next time. But read access is, normally, neither necessary nor desirable.

Edit: Oh, you did mention that "it didn't work." Perhaps you wanted to use the -R option to apply you changes to the subdirectories and files of /lib. See man chmod for details.

I'm stupid... :P Thanks

6 = read & write permissions; but you are talking about a directory; and a directory is completely useless without execute permission, because it is execute permission which allows access to its contents. Even without read and write permissions, if a directory has execute permissions, then you can still access everything inside if you know their names; but without execute permission you can do nothing. I suggest you give the directories something like 755 or 711 permissions.