I am aware of only two causes for the Oracle error code ORA-00942
The table (or view) really doesn't exist
The database user does not have permission to access (or modify) the table
Since you claim to be able to modify the table via TOAD but not via Hibernate, my guess is that you are using different database users in TOAD and Hibernate.
Also, when accessing a table in Oracle, you only really need to prefix the table name with its schema name if you are accessing it from a different schema.