Hi Joost,
You were right, it was the system clock. It's working now.
For any one following this thread this is what i did:
run:
apt-get install netdate
netdate tcp 128.2.136.71
Create /var/spool/cron/tabs/root:
# update time with ntp server
0 3,9,15,21 * * * /usr/sbin/netdate 128.2.136.71
Then run
chmod 600 /var/spool/cron/tabs/root
/etc/init.d/cron restart
regards,
sybella.