If you are using Alex popularity plug-in then you might face this error while upgrading plug-in automatically in WP 2.5. This error generate due to invalid wp-header file path in plug-in file. Unfortunately, Alex not released new fixed version of the this popular plug-in. However, fix is really very simple and anyone can fix issue just by editing one single plug-in file. Please follow steps below to fix this error in your installation:

  1. Deactivate older version of the plugin. If you are installing first time skip this step.
  2. Download the latest release from wordpress.org or plugin author website.
  3. Open popularity-contest.php in your favorite editor and scroll down to line 59. Replace
    require('../../wp-blog-header.php');

    with

    require('../wp-blog-header.php');
  4. Save file and upload file to your plugins folder.
  5. Reactivate the plugin

Written by Bala Krishna

Bala Krishna is web developer and occasional blogger from Bhopal, MP, India. He like to share idea, issue he face while working with the code.