Recently, a customer dropped off a three-week-old iMac for an issue he was having with the optical drive. Every disc inserted into the drive would return an error of: “The disk you inserted was not readable by this computer.” Normally, this is a message that will pop up when an unformatted hard drive or thumb drive is attached to the computer, but not a DVD or CD.
We checked in the iMac and I began my testing. When the system was booted to a known-good volume, the optical drive functioned perfectly. This immediately shifted my focus to that of a software issue, rather than hardware. A software issue that solely affects the optical drive is somewhat rare, so I knew some Apple forum digging would possibly help out.
The issue persisted after creating a test user account, telling me that this was a system-wide issue, not at the user level. A lot of times, with software issues like this, it’s much less time consuming to simply restore the operating system and migrate the data back over. This has fixed countless system-wide software issues, and allows us to get the computer back to the customer in a timely manner. However, I try to do a little bit of research on the issue first when it’s this specific.
I came across an Apple forum discussion on the topic, with one user explaining that he deleted a certain Kernel extension file, which resolved the issue. The file was named “LexarFilterScheme.kext”, presumably having some relation to a Lexar product. I researched this specific Kernel extension file a little further, and discovered that this file, when installed, will prevent the optical drive from functioning. Apparently, this issue has happened to a handful of users.
I first copied the kext file to a flash drive (just in case), and then deleted it from the “/System/Library/Extensions” folder. After a quick restart, the optical drive was back to normal, reading discs as it should be.
Apparently, this corrupt Kernel extension is packaged with the install of “Secure Vault,” a piece of security software that comes pre-installed on some Lexar flash drives. Unfortunately, the Lexar software will not work properly after removing this file, but there are many other options as far as security for your flash drive, such as creating an encrypted disk image on the flash drive using Disk Utility.