title: What is this bug in IntelliJ IDEA?
body: <p>When I try to edit and save a javascript file, IntelliJ makes it impossible:</p>
  
  <p>Cannot save C:\Users\dev\joo-web\trunk\joo-admin-web\src\main\webapp\scripts\extjs\examples\tree\treegrid.json.
  The file was renamed to treegrid.json_<strong>jb_old_</strong>.
  Your changes were written to treegrid.json_<strong>jb_bak_</strong>.</p>
  
  <p>Why has this happened? What is possible to do to fix it?</p>