Loading Oracle JDBC drivers inside Scriptmaster

This code (with the return replaces by println) works fine in Netbeans, but not when evaluated within Filemaker. I am loading the Oracle JDBC JARs (the Java 6 jar ojdbc6.jar and orai18n.jar) - which JDK does Scriptmaster use? Am I missing something obvious?

import groovy.sql.Sql;

import oracle.jdbc.OracleDriver;

def town = 'Birmingham';

def sql = Sql.newInstance("jdbc:oracle:thin:@192.168.1.192:1521:orcl", "username",

"password", "oracle.jdbc.OracleDriver");

firstRow = sql.firstRow("select * from customers where postaltown=${town} order by surname");

return "${firstRow.forename} ${firstRow.surname}");