The /mnt/ext is mounted to an ext2 filesystem, an external hard drive. For some reason I can't run scripts from there. Please see the session below.
luntain@plato /mnt/ext $ echo "echo success" > k.sh
luntain@plato /mnt/ext $ chmod 777 k.sh
luntain@plato /mnt/ext $ ./k.sh
-bash: ./k.sh: Permission denied
126luntain@plato /mnt/ext $ ll k.sh
-rwxrwxrwx 1 luntain luntain 13 Jan 23 15:08 k.sh*
luntain@plato /mnt/ext $
I would love to find out why I see the error.