[SOLVED] No Write Permission for Root User

[raspifreak]

Software
XBian version: 1.0RC2
XBMC version: 13.1-BETA1
Overclock settings: default

Hardware
Power: 5V 2A
RPi Model B+
SD SanDisk class 10 - 16GB
LAN
Connected TV, USB

Problem description:
I have successfully installed and tested ssmtp in my xbian system. The problem is that I receive a bunch of emails each minute
as defined in my /etc/crontab (reset, kill, check and get), unless I stop it using:

Terminal

sudo service cron stop

Normally, if I set the "MAILTO" to an empty string, the problem is solved, however I have no write permissions to modify the file crontab.
I have already tried modifying

Terminal

sudo nano /etc/crontab

as the default "xbian" user as well as " nano /etc/crontab" by logging as root, still no permission to write.
Although finally I could successfully modify "crontab -e" (i dont really understand the difference between this command and the normal nano or vim access), the spam emails kept coming

Google says it's something about file attributes, some people solved using a "chattr" command but it didn't work on Xbian

Any solutions for this annoying problem ?