If you set the Content Type drop-down (bottom right of the window) to it will stop happening.
Alternatively, drop back to 9.5.0.0 for now (e.g. if you want to use the Content Type feature).
This bug is new in 9.5.1.0 and only affects new users who turn on Content Type detection for the first time. For now, GPSoftware have reverted the main download page to 9.5.0.0 to avoid the problem until a fix is ready. Existing users who still want 9.5.1.0 can get it via the link in my signature.
I've updated the relevant FAQ to point to this thread to help anyone else affected.