FB,
i was very excited to encounter your ideas about how to fix a similar problem I was having. I (stupidly?) decided to enable firevault on my mid 2013 Air
running Yosemite today . initiated the process on 17% battery, was Told to connect to power source but I noticed that making the connection didn't change the phrase on the screen that should have recognized I had connected it (or something,i was not paying close attention at the time). Stupidly again, because i approach apple products with the false expecitation they will 'just work', i went ahead with generating recovery key etc. On restart, ive now had 10 hours of continuous black screen with pinwheel spinning. Not knowing if this was part of the "patience" required I waited a very long time. finally, decided to restart in safe mode, which was sluggish and just as my custom wallpaper would appear it would be polluted by flashes of horizontal bars and static but would load. Each time I would return to the blank screen after running safe mode. But I've been fiddling with my wallpaper for months and had it changing every 30 minutes. after reading your post, I went in again and ONLY changed the wallpaper (deleted new files that I had added and returned it to the Yosemite image). And just like that, I had a normal restart, fire vault appearing to BEGIN encrypting (goodbye 10 hours of waiting, hello 14
more), and its now the recognizing power appropriately. Thank you to you and to everyone participating in this discussion. Forgive me if a few pages down this is all been clarified and refined. Id say if you've come this far and youve been adding wallpaper files just try this fix in safe mode before wiping or Reinstalling anything! - cheers from NYC