Adding or editing the IP address on a Solaris 10 server is different from the previous versions of the OS (Solaris 9, Solaris 8 etc).
In the previous versions of the Solaris Operating System, you need to edit the /etc/hosts file and add/edit the entry for the IP address and the hostname.
However, in Solaris 10, you should edit the /etc/hosts file (a symlink to /etc/inet/hosts file) and the /etc/inet/ipnodes file and add an entry for IP address and hostname.
Once done, restart the Network service using
# svcadm restart network/physical
or reboot the server for the changes to take effect.
Although, the /etc/inet/ipnodes files is primarily for IPv6 only, without adding an entry to the file, the IP address (IPv4) doesn't become active. This seems to be a known problem but the good news is this is now fixed in the Solaris 10 U4 (08/07 build).
Also, ensure that the /etc/netmasks file with the network ID and the netmask.