I would take a look at this StackExchange thread and the linked articles contained: Is File Vault 2 whole disk encryption or whole partition encryption?
Assuming what you are aiming for is an encrypted Lion partition and an unencrypted Linux partition, the decrypt, partition, encrypt process described will accomplish what you are looking for.
As always, back up first.
Suggestions
Review System Preferences
Create another user.
Log in as that user.
Use the Security & Privacy pane of System Preferences. In the FileVault tab, click Enable Users… then in the sheet, ensure that all required users are enabled.
Hint
System Preferences may show that FileVault is enabled, with a recovery key, when there is encryption with Core Storage, but neither FileVault 2 nor a recovery key. I reported this bug to Apple a while ago.
Similarly, but not the same bug:
- I assume that System Preferences may show FileVault disabled on a system where most elements of FileVault are enabled.
Thorough application of Disk Utility
Ensure that the utility is applied:
- to the logical volume group, which appears to contain the logical volume.
(Where Core Storage is used, Disk Utility in 10.8 can not show the physical disk.)
If you select the LV alone, then verification will omit the partition map.
Observations
Conversion Status: Failed
If encryption was applied when the volume was created (typically: erasure with Disk Utility) then:
- there was no conversion forward
- conversion backward can not begin.
Conversion Direction: backward
This implies that:
- recently, conversion backward did begin
- previously, the logical volume was the result of conversion forward (not the result of erasure with Disk Utility).
diskutil coreStorage encryptVolume 4FDED44E-EC4B-4B11-9FF5-9C958BD8CEAB
That could apply if logical volume 4FDED44E-EC4B-4B11-9FF5-9C958BD8CEAB was not encrypted.
As the LV is already encrypted, the response from diskutil is correct.
The question in Apple Support Communities
From the opening poster:
Does the resolution there in ASC, the bounty here in Ask Different, mean that Dennis continues to seek a more detailed answer, a better resolution?
Code -69755
-69755 appears in another discussion:
Interpreting the failure
Pessimistically but realistically:
- a failure to convert – with conversion of nothing – may indicate media failure, possibly in or around the area occupied by the extents file.
Best Answer
When you say you decrypted it momentarily, it can take from minutes to days depending on the size of the partition and data within it and the speed of your system. The same goes for encrypting. The amount of free space also impacts how long things will take as it needs to encrypt/decrypt files somewhere.
It could be the case that it hasn't finished decrypting it yet.