After upgrading to WordPress3.1, many users experienced broken permalink issues. Some users were able to identify the Simple Tags or Top Level Category plugin as the culprit. In this case, obviously, the culprit is the Multi-page Toolkit plugin. http://solidlystated.com/scripting/wordpress-3-1-permalinks-broken-multi-page-toolkit/

The Quick and Easy Fix

The following simple fix was identified by WordPress.org member docarzt, so I cannot take credit for it. You simply need to delete one line of code.

This fix applies to Multi-page Toolkit version 2.6 and a newly upgraded WordPress 3.1 installation.

Please note that the broken plugin may cause WordPress to act strangely. Disabling the plugin may not immediately cause your broken permalinks to appear fixed. Likewise, the fix may not appear to work after reactivating the plugin. I was able to simply wait a minute to verify that it righted itself.

Find the allpage_permalink() function in TA_multi_toolkit.php in the plugin’s folder.

PHPview code 
function allpage_permalink() {
    global $wp_rewrite;
    $wp_rewrite->add_endpoint("all", EP_ALL);
    $wp_rewrite->flush_rules();
    ...
}

Delete the line $wp_rewrite->flush_rules(); and you are done.

If you have broken permalinks after your WordPress 3.1 upgrade and you have neither the Multi-page Toolkit or Simple Tags plugin, you should definitely try disabling all your plugins to see if that repairs it.

Then, you can turn them back on one at a time and find the one that causes you heartache.

Good luck! If you identify any other broken plugins, comment about them below to help other users… at least until we get some proper plugin updates released.

List of reported broken plugins at WordPress 3.1 launch:

  • Simple Tags
  • Multi-page Toolkit
  • Top Level Categories
  • Featured Content Gallery
  • Simple Sidebar Share Widget
  • Advanced Permalinks
  • Qtranslate