Two possible reasons for the errors:
1. ORA-00942: table or view does not exist often means the user, TESTPORTAL in your case, does not have access (select, update, etc.) to the table. Unfortunately, the message fails to inform you what table is either missing or not accessible.
There are a few tables such as the HILOSEQUENCES and TIMER tables which may not have been created in the TESTPORTAL schema and are there for not accessible by TESTPORTAL. I offer this as an example as I do not know if these two tables are even used by the portal.
The default install of jboss portal uses the HSQLDB with the sa account which I believe has DBA-like authorities -- can access virtually anything. I suspect your TESTPORTAL might not have broad enough rights to access one or more tables in the database.
It would be great if someone could offer up the specific rights requried by the portal account. The user guide simply says create an account and everything else is automatic. This works if the account is granted sufficiently broad rights.
2. I have noted error messages such as the ones above on the initial start-up of the portal against an empty database. Once the tables have been created and initialized, subsequent start-ups do not log any such errors. In this case, the tables may truly be missing and the initial start-up responds by creating the missing tables, explaining why subsequent start-ups proceed normally without errors.