The problem is solved, what i did was to boot with single mode (command+s) and follow the instructions below from NUMBER 6 '''Reset certain privileges''' in '''Your Mac won't start up in Mac OS X (Mac OS X 10.3.9 or earlier)''' at
http://support.apple.com/kb/TS1411?viewlocale=en_US
1. Start up the computer in Single-User Mode.
2. Check the volume with fsck.
3. Type: mount -uw /
4. Press Return.
5. Type: chmod 1775 /
6. Press Return.
7. Type: reboot
8. Press Return.