Created attachment 107455 [details] screenshot of the unresponsive window. (this happens only on latest version of kdenlive) to reproduce start latest KDEnline on Windows 10 64.. try to place an MP3 using drag'n'drop .. after that the application become irresponsive. .. it's necessary to kill the app. (no icon of the MP3 diplayed)
Solved on laetst build for Windows (by Vincent) 17.08.1