Google announced on Google+ that they are discontinuing support for the AdWords Editor version 10.6 or older. Google is encouraging all advertisers who use the AdWords Editor to upgrade to version 11.1 by June 30th, 2015.
In December 2014, Google launched a major revamp for the AdWords Editor, version 11. It is so different that Google must be finding it inefficient to manage version 10.x, so they are going to stop supporting 10.x and make people migrate to version 11.x.
Google said on Google+:
In December last year, we introduced the most significant update to AdWords Editor since the tool was first released [http://goo.gl/umFOzq]. In addition to a visual redesign and faster interface, we enhanced the features you know and love while also adding new ones to help you do more in less time -- from managing multiple accounts side by side to opening up multiple windows to managing labels at scale.
Starting June 30th, 2015, AdWords Editor versions 10.6 and older will no longer be supported. To ensure uninterrupted use of AdWords Editor, you will need to upgrade to version 11.1 before June 30th, 2015.
You can upgrade over here.
Forum discussion at Google+.