Try entering the following sql statement for the portal database:
insert into jbp_role_membership (jbp_uid,jbp_rid) value (1,1);
That should re-establish the relationship between the admin user and the Admin role.
By the way, you never said which version of the Portal you are using, or hwich database. The above assumes Portal 2.4GA, not sure it it works on any other version.