Error in compilation

[Marcos Antonio]

Hello, everybody!
 
I'm getting this error when compiling my application:
 
An exception has occurred in the compiler (1.7.0-internal). Please file a bug at the Java Developer Connection (http://java.sun.com/webapps/bugreport)  after checking the Bug Parade for duplicates. Include your program and the following diagnostic in your report.  Thank you.
com.sun.tools.javac.code.Symbol$CompletionFailure: class file for com.sun.runtime.ProxyHelper not found

I suppose that the ProxyHelper class isn't in my classpath. So I would like to know in which jar I can find it. This is my ant script used to compile:
 
<?xml version="1.0" encoding="UTF-8"?>
<project name="desenvolvimento" default="empacotar">
 <property name="patched.javac.jar" location="C:/lambda/langtools/dist/lib/javac.jar" />
 <property name="jar" value="C:/desenvolvimento/sistemas/sistema/desenvolvimento.jar" />
 
 <presetdef name="patched.javac">
  <javac classpath="C:/desenvolvimento/sistemas/sistema/commons-codec-1.4.jar" fork="yes">
   <compilerarg value="-J-Xbootclasspath/p:${patched.javac.jar}" />
  </javac>
 </presetdef>
 
 <target name="compilar">  
  <patched.javac srcdir="." />
 </target>
 
 <target name="empacotar" depends="compilar">
  <jar destfile="${jar}" filesetmanifest="merge">
   <fileset dir="." includes="**/*.class" />
   <fileset dir="." includes="META-INF/**" />
  </jar>
 </target>
 
 <target name="executar" depends="empacotar">
  <java jar="${jar}" fork="true" />
 </target>
</project>
 
This error appeared when I introduced defender methods in my code. Before them, everything was working fine.
 
Thank you in advance.
 
Marcos