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I decided to enable full disk encryption using FileVault2 in OSX Mountain Lion, but near the end of the encryption process, I get a message telling me that it failed, and that I should disable and reenable it to try again. When I try to disable it I get an error: An error occurred while reverting the disk. (Error: -69755). So I am stuck in a vicious cycle. Luckily, the drive is still accessible and usable, but it's clearly not encrypted.

Here are screenshots of the process:

enter image description here

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I would prefer to avoid reformatting the drive (it's a single partition).

There is a long thread in the Apple Support Communities, but there is no acceptable answer so far.

share|improve this question
Restore from the backup that you certainly would have taken before starting this process. – Daniel R Hicks Dec 17 '12 at 1:05
@DanielRHicks My backup process involves manually keeping files of interest on an external drive and working files in the cloud, so while I have the ability to recover all data that is important to me, it is not a full backup, so I cannot restore. – Ben Mordecai Dec 17 '12 at 2:11
Yet you started an encryption process that mucks with the entire disk? – Daniel R Hicks Dec 17 '12 at 19:54
@DanielRHicks I'm not willing to buy a new external drive right now that could fit a full backup, so I only back up the files that can't be recovered by a new installation. I back up for crisis scenarios, so a mildly inconvenient recovery process is not a problem for me. More importantly, I was hoping to actually learn something about the issue. So do you have any idea what's going on or are you just here to badger me about my backup methods? Couldn't almost every system troubleshooting issue be fixed by restoring from backup? – Ben Mordecai Dec 17 '12 at 23:25

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