Problem in populating tables

To populate the tables of a database ( drawn from a book )I
have followed two strategies.
The first one :

1)I create the tables without any definition of foreign keys.
2)I have altered the tables to add the foreign keys.
3)I populate the tables obtaining error ( obvious ).

The second one :

1)I create the tables without any definition of foreign keys.
2)I populate the tables without obtaining any error.
3)I have altered the tables to add the foreign keys with three
error out seven ALTER TABLE --- .

I think that the sql to create and alter the table is lawfull
because in the first try the steps 1) and 2) execute flawless.

Then where is the problem ?

In sqlcode.txt there is the sql to create and alter the tables.

In error.txt there are the reported errors.

The postgresql version is 7.2.2 on a Mandrake 9.0.

Thanks.