title: Missing required library in eclipse for non-required library
body: <p>I'm using Eclipse for Java Develepers (Juno x64 running on Windows 7).</p>
  
  <p>I have a project in which I was trying out a jar I no longer need (args4j), so have removed the dependency.  At some point, my PC lost power unexpectedly, and I've since restarted Eclipse.</p>
  
  <p>My project now has an error, <code>"Project 'MyProject' is missing required library: '/path/to/args4j-2.0.21.jar'"</code>.  I was working with the project for some time after removing the dependency without any issues.</p>
  
  <p>Under the Project Properties > Java Build Path, there's no reference to args4j in any of the tabs.</p>
  
  <p>I've tried:</p>
  
  <ul>
  <li>searching for the string "args4j" in all files within my project, but there are no matches.  There <em>are</em> a bunch of references within <code>&lt;workspace&gt;\.metadata\.plugins\org.eclipse.core.resources\.history\</code>, but I'm reticent to touch them out of fear I might break something else.</li>
  <li>[Edit] clean rebuild has no effect.</li>
  </ul>
  
  <p>Does anyone have any idea why Eclipse is complaining, and what I might be able to do to fix it?</p>