Same issue as Michael.
WAB 1.0 Dev Edition freshly installed from Web AppBuilder for ArcGIS (Developer Edition) | ArcGIS for Developers (today)
The locale is French. Cache cleared. Server stopped/started after the first time the issue happened, just in case.
All starts fine until the welcome page. I hit "create" and fill in the fields. Neither OK nor Cancel do cause any action, apart of the whole dialog box getting surrounded by a blue rim. The dialog box can be closed with the cross icon in the top right corner. I observe the same behaviour in the "import" dialog box : OK and Cancel have no effect whatsoever.
NOTE : issue seems to be Chrome only.
Regards,
Matt