taskdef class org.programmerplanet.ant.taskdefs.jmeter.JMeterTask cannot be

[samdanield]

<project basedir="/home/ubuntu/apache-jmeter-2.7">

 <property environment="env"/>
  <property name="jmeter-home" location="/home/ubuntu/apache-jmeter-2.7"/>

  <path id="ant.jmeter.classpath">
    <pathelement
       location="${jmeter-home}/lib/ant-jmeter-1.8.4.jar" />
  </path>


      <taskdef
        name="jmeter"
        classname="org.programmerplanet.ant.taskdefs.jmeter.JMeterTask"
        classpathref="ant.jmeter.classpath" />


  <target name="clean">
    <delete dir="results"/>
    <delete file="jmeter.log"/>
    <mkdir dir="results/jtl"/>
    <mkdir dir="results/html"/>
    </target>


 <target name="test1" depends="clean" >
     <jmeter jmeterhome="/home/ubuntu/apache-jmeter-2.7"
        resultlogdir="results/jtl"
       testplan="/home/ubuntu/pt/********.jmx" />
 <xslt
    in="${basedir}/results/jtl/********.jtl"
     out="${basedir}/results/html/*********.xml"
     style="${jmeter-home}/extras/jmeter-results-report_21.xsl"/>
 </target>
   </project>

when i build this file its showing the error asbuild.xml:14: taskdef class org.programmerplanet.ant.taskdefs.jmeter.JMeterTask cannot be found using the classloader AntClassLoader[]

any ideas regarding this will be of great help.

Regards,
SD