Problems in Building Duke's Bank Sample Application of J2EE Tutorial from Sun

Hi,
When trying to build the duke's bank application I am getting the following error
ant compile-ejb
"Error's Seen are "
Class org.apache.tools.ant.taskdefs.Copy doesn't support the nested "mapper" element.
Build Failed.
Any solution to resolve the problem is highly appreciable.
I am building it under Windows NT4.0 environment.
I ensured the following environmental variables are set properly
ANT_HOME
J2EE_HOME
JAVA_HOME
CLASSPATH
Thanks,
Vishy