It could be Memory issue , Portal requires :
1.5 Gbytes of RAM for regular deployment on Sun Java System Web Server
2.0 Gbytes of RAM for regular deployment on Sun Java System Application Server
and double of RAM size , swap space.i.e around 3GB or 4GB
You can create swap space on solaris using following instruction:
http://docs.sun.com/app/docs/doc/819-2723/6n50a1n3v?a=view
If you memory is fine then.
Please check installation log files at following dir:
/var/sadm/install/logs.
From this log file you can ensure that whether Package installation went fine or not.
If that is fine then you need to have look as configuration log file at location.
/var/opt/SUNWportal/logs/config/portal.fabric.*.log
and
/var/opt/SUNWportal/logs/admin/portal.0.0.log.
This logs files will give clear information about what went wrong.