title: "duplicate entry" error when exporting Java project to JAR with Eclipse
body: <p>I am trying to exort a Java project with Eclipse 3.6.1 to a runnable Jar. This used to work properly but failed today, afer I added some additional Jars to my class path.</p>
  
  <p>The error is</p>
  
  <pre><code>duplicate entry: some/class.class
  </code></pre>
  
  <p>Interestingly, there is a duplicate entry for almost any class in my buildpath. Even though I did not change anything. The Jars I added do not contain duplicate classes.</p>
  
  <p>Question: Is this some kind of Eclipse bug? Am I ovrlooking something obvious? Does anybody have an idea what could cause this error?</p>
  
  <p>Cheers</p>