Mouse configuration gone awry

While editing a Leafpad entry, I discovered that my usual method of sweeping the
cursor over the text preparatory to selecting & cutting it for export to another
instance of Leafpad simply wipes out the selected field.

In another instance of Leafpad, the mouse behavior is normal.

The text in question was a set of absolute paths to log files on my hard drive.

I cannot find either a Leafpad or a mouse configuration file in /etc.

The 'puter is a Thinkpad T420 running trisquel Etiona, installed yesterday.

Thanks,
George Langford