Source : EA.com

This error often occurs when the Playstation 2 is having trouble logging onto the internet service provider. Please make sure the network adapter is properly configured for use online. Also, try out other online games for the Playstation 2 and see if they work or not. For further information about going online with Playstation 2 games please visit the following web site.

http://www.us.playstation.com/support.aspx

If the system is unable to connect online with any of the Sony PS2 online titles due to a DNAS error, please contact Sony for assistance in configuring the network file. The phone number for the Sony support team is 1-800-345-SONY (7669)