immediate hang on clicking "preferences"

I was changing around the interface, or at least trying to.
Something was changed - Calibre now immediately hangs when I select the preferences icon.

Selecting "run welcome wizard" or "run in debug mode" will work. Selecting the icon, or change Calibre behavior immediately hangs Calibre - must be killed with task manager.

I tried repair (under Windows) and tried re-installing latest release (3.14) - makes no difference.

I keep pretty current backups of everything - perhaps there is a preference file I could restore from a few days ago, if I knew where the file was (since I can't use Preferences to tell me where it is)

All other functions I have tried seem to work fine.

Suggestions please??? Or a location of the file if restoring is it likely to work.

Windows 7, Calibre 3.14

thnx,


.