My sites are down also. Here is a message I got from them.
The maintenance scheduled for Friday, March 14, 2008 from 12 AM to 6 AM EST was canceled and rescheduled for Sunday March 16th from 12 AM to 6 AM EST. NationalNet will be performing maintenance on portions of the network. While we do not anticipate any downtime during this period, it is possible may experience difficulty reaching your website(s) or server(s) during this time. Should you have any questions regarding this, you can contact us by submitting a ticket at
http://support.icertified.net or call our support line at 1.800.547.9995 (international 1+909.370.2911)