I've not worked with Oracle but I'll give this a shot. Try the following:
1) If the database you are querying is transcational, add the text (without quotes) "WITH (NOLOCK)" as part of your FROM clause. It may be possible for your DBAs to have set that any queries run without this to be rejected since it would result in locking the table.
2) I assume, by your query, that custId is of an integer type but if it is varchar (String) then make sure to put your single quotes around the parameter afte the '='.
I would ask the following:
Where are you firing the query from? Are you doing it as part of a webservice the form is connected to or are you doing it inside Workbench using one of the JDBC services (or another means)?