I have a server with server matrix..

Some of my friends have bad 'page not found' errors on my server. I think its something to do with the DNS setting, sometime my server works, sometime it dosent.

The IPS always work.

http://69.56.198.154
http://69.56.198.155 << site forums

These are the mainsites that are sometimes affected by these errors.
http://l337admins.com
http://og-network.com
http://og-n.com
http://og-forums.com

Any idea?