Im trying to insert data in two databases configured in the same computer running SQL Server 7.0

The connection to both databases is right and theres no problem on it.

Both databases have the same structure, tables, stored procedures, users and any other items configured in the same way ( Im sure about this because one of them is a database on a production envionment and the other one is a trial database used to work as a previous step to go to the production environment ).

The problem becomes running any single insert statement.
In the proval database it runs OK and inserts data and desired but when I run the same query in database B it doesnt insert nothing and reports sqlerror code 100.

I want to know if anyone has listened about a problem like this because Im getting a little crazy with the problem.
Why SQL reports this errorcode ?

Thanks in advanced to everybody