2 Replies
Jerry Beaucaire

Corruption in a slide or two I would guess.   One way to possibly locate it sort of quickly:

  1. Duplicate your troublesome course
  2. Confirm it still won't preview
  3. Delete the last slide, preview
  4. Keep repeating step #3 until you finally get a successful preview.  That means the last slide you deleted was an issue.
  5. Reopen your original file and recreate the troubled slide, try to preview.
  6. If it works, you're good.  If not, then more than one slide may be at issue, start again at step #1 to find the next troubled slide.   

Hopefully it won't be too many of them.