Vignette all of a sudden applied to ALL of my photos.

ponalizer  wrote I can of course manually remove the effect from each one of the pictures, but this would take aaaaages!

You can also remove the Vignetting settings from ALL 65,000 of the image files using Develop module Sync with just that setting checked. Just keep in mind you will lose the Vignetting settings on image files you have actually applied and want the effect on.

Or as suggested by Hal P Anderson restore the LR catalog using your latest backup file. Doing so will lose any edits and imports made AFTER the backup date. You'll then need to reimport or Synchronize folders to get the new files into LR and then reapply edits made to ANY of the image files after that date.

Choose the "lesser of evils."

Just Shoot Me is probably right. If you have a recent backup, restoring that would probably save you the most work.

Hal