The quickest way to resolve your issue is to manually assign the address.

I assume you can open a terminal session using telnet, ssh or (xterm at the console).
use smitty tcpip at a # prompt
choose Minimum Configuration & Startup
choose en0 as the network interface (unless you have evidence that it should be something else)
fill in the blanks with
hostname (can include domain name)
gateway
DNS servers
etc
Your connection type should probably be dix or tp. I would not change from default.

Note: Some will say this should only be used once at initial setup of the server. Use outside that initial time frame can corrupt your ODM. (ODM is the configuration database for AIX.) It has been my experience at AIX 5.2 and later that you can make changes here and not experience corruption.

I would consider it best practice to staticly assign an IP address to a server.