I created all the tables and objects needed by base.but when I visit first page from browser(http://localhost/base) ,It always display "The underlying database xmgora@localhost appears to be incomplete/invalid. The database version is valid, but the BASE DB structure (table: acid_ag)is not present. Use the Setup page to configure and optimize the DB.".
  When I click the "setup page" link,It display:

   Unable to CREATE table 'acid_ag': Database ERROR:ORA-00955: name is already used by an existing object

Unable to CREATE sequence 'snort.seq_acid_ag_id': Database ERROR:ORA-00955: name is already used by an existing object

Unable to CREATE trigger 'tr_acid_ag_id': Database ERROR:ORA-24344: success with compilation error

Unable to CREATE table 'acid_ag_alert': Database ERROR:ORA-00955: name is already used by an existing object

Unable to CREATE table 'acid_ip_cache': Database ERROR:ORA-00955: name is already used by an existing object

Unable to CREATE table 'acid_event': Database ERROR:ORA-00955: name is already used by an existing object

Unable to CREATE table 'base_roles': Database ERROR:ORA-00955: name is already used by an existing object

Unable to INSERT roles: Database ERROR:ORA-00911: invalid character

Unable to INSERT roles: Database ERROR:ORA-00911: invalid character

Unable to INSERT roles: Database ERROR:ORA-00911: invalid character

Unable to INSERT roles: Database ERROR:ORA-00911: invalid character

Unable to CREATE table 'base_users': Database ERROR:ORA-00955: name is already used by an existing object

when I click "search" link ,it display:

Database ERROR:ORA-00911: invalid character

somebody can help me!?thank you very much