You have been directed here because you are using an old version of the Twinkle scripts. A new version for SEWP has been available since September 2012 and brings many improvements, whereas the old version is no longer maintained and has become more and more outdated and broken. For that reason, the old scripts have now been deactivated.
To load the new Twinkle, simply activate the Twinkle gadget in your preferences.
Stop loading the old Twinkle scripts
The message that brought you here is shown because you are still loading one of the old scripts in one of your user script files. To stop that, edit that script file (typically Special:MyPage/skin.js, but possibly Special:MyPage/common.js) and remove all script imports of Twinkle or Friendly, like: importScript('User:EhJJ/twinkle.js'); importScript('User:LightForce/twinkle.js'); If you need assistance, do not hesitate to ask at Wikipedia talk:Twinkle.
Twinkle features a brand-new GUI preference panel. Once you've installed the script, you can set your personal settings at WP:Twinkle/Preferences.
Users of the new Twinkle will be able to take advantage of many improvements, including:
Transition to the MediaWiki API. Previously, Twinkle used to download the same editing form as is used by human editors, fill it out behind-the-scenes, and send the request back as if the "Save page" button had been clicked. This was unreliable – if the format of the edit form was modified, or if malformed editnotices were present, Twinkle failed. Now, Twinkle uses the MediaWiki API to edit pages, a more solid approach specially designed for programs and scripts like Twinkle.
New look. Twinkle now has a refreshed look, based on en:jQuery UI.
Now works on Internet Explorer 9 (with very minor limitations, e.g. not being able to move the dialogs).
Lots of new features. You can now: preview user warning templates before posting the warning; enable a "userspace log" to keep track of your speedy nominations; and customize your Twinkle easily, with a graphical interface instead of editing code (see WP:TWPREFS).
Lots of new admin stuff. Admins can now: rest easy when protecting using the PP tool - it has been redesigned, and you have full control over what it does; opt not to delete the talk page and/or redirects when using the CSD tool; edit the deletion reason before deleting with the CSD tool.
And lots more minor annoyances and nits have been fixed.