Comment 5 for bug 861930

I can confirm that the temporary workaround provided by Graham Waugh in #4 above works. Before I made the change to the LangCache.py file, accessing System Settings > Locale > System Languages would result in an error about a KCModule. Closing System Languages then resulted in a crash of System Settings.

After making the change to line 41 and rebooting, I got no error and accessing System Languages asked me if I wanted to download the languages. I acknowledged, the download took place, and I was then able to set my default system language to English (United States).