title: 'Execution failed: Data storage error' on setProperty
body: <p>On a script which has been working fine for some time and unchanged, today I get </p>
  
  <blockquote>
    <p>'Execution failed: Data storage error'</p>
  </blockquote>
  
  <p>on a line which consists simply of:</p>
  
  <pre><code>PropertiesService.getScriptProperties().setProperty('runMode', 'LIVE');
  </code></pre>
  
  <p>What can I do to fix this? <br/>
  <strong>Is this some kind of server error?</strong></p>