title: All Plugins Deactivated and Cannot Install The Plugins in WordPress
body: <p>When I login into wp-login <strong>(WordPress 3.6.1)</strong>, I found that all my Plugins are deactivated.</p>
  
  <p>Error message after wp-login:</p>
  
  <p><strong>The plugin user-locker/user-locker.php has been deactivated due to an error: The plugin does not have a valid header.</strong></p>
  
  <p>Then I try to install any Plugin, but failed.</p>
  
  <p>Error message when install Plugin:</p>
  
  <p><strong>Downloading install package from <a href="http://downloads.wordpress.org/plugin/user-locker.1.2.zip" rel="nofollow">http://downloads.wordpress.org/plugin/user-locker.1.2.zip</a>…
  Download failed. Could not open handle for fopen() to /tmp/user-locker.tmp</strong></p>
  
  <p>But I check my website still running normal, not blank.</p>
  
  <p>Kindly need assist to solve this issue.</p>
  
  <p>Thanks.</p>