title: Intellij Error: Internal caches are corrupted or have outdated format
body: <p>I am getting an error intermittently when I build my Java project in Intellij.</p>
  
  <p>Internal caches are corrupted or have outdated format, forcing project rebuild: java.io.FileNotFoundException: C:\target\classes\ehcache.xml (Access is denied)</p>
  
  <p>I have run File->Invalidate caches. I have restarted Intellij and killed all Java processes. I eventually get it to build again but not sure what thing I try does the trick.</p>
  
  <p>When I try to access the 'Target' folder, it says Access Denied.</p>
  
  <p>Anyone seen this before?</p>