Keyboard settings not saving

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Open Finder, press Option key, select Go > Library, open Preferences and delete com.apple.systempreferences.plist

Reset PRAM and SMC, and go to System Preferences > Users and Groups, create an user and see if it appears.

http://support.apple.com/kb/PH11243

http://support.apple.com/kb/HT3964?viewlocale=en_US

Press Command and R keys in boot and reinstall

I have exactly the same problem and it's confused me since I upgraded my system to Mountain Lion. I once phoned Apple customer service but they didn't have any clue either. I was really disappointed by them.

Now, I think I found the root cause: it's due to the case-sensitive filesystem. I used to configuring my hard drive as a case-sensitive filesystem. However, after installing OS X 10.8 on an external USB hard drive with being formated as a case-insensitive filesystem and booting from it, all the problems simply disappeared. I also found some logs on the Console:

27/08/12 8:55:07.467 AM System Preferences[296]: Unable to open IOHIDSystem (e00002bd)

27/08/12 8:55:07.000 AM kernel[0]: virtual bool IOHIDEventSystemUserClient::initWithTask(task_t, void *, UInt32): Client task not privileged to open IOHIDSystem for mapping memory (e00002c1)

27/08/12 8:55:07.468 AM System Preferences[296]: ASSERTION FAILED: gALSPlugin != ((void*)0) copyPreferenceForKey line: 230

27/08/12 8:55:07.468 AM System Preferences[296]: ASSERTION FAILED: gALSPlugin != ((void*)0) copyPreferenceForKey line: 230

Let's hope Apple fix this soon...

I was disappointed as they just recommended me to re-install the operating system, which made me think of some funny opening video in some Apple conference; do they want to be as stupid as Mxxxxsoft?

I have the same problem - automatic screen brightness and keyboard brightness are both broken since I installed mountain lion. And I also use a case sensitive filesystem. I just updated to 10.8.1 and there is no improvement.

I have the same issue although the line is different.

8/31/12 1:44:29.100 PM System Preferences[12726]: ASSERTION FAILED: gALSPlugin != ((void*)0) setPreferenceForKey line: 248

After upgrading to OS X 10.8.2 the problem remains.. 😟

So far, this error also appears in the console when increasing/decreasing the keyboard backlight.

I've got a mid-2012 MacBook Air and the same problem. I tried re-installing the newest version of 10.8 (case-sensitive HFS+), resetting SMC and PRAM. No luck. Incredibly annoying.

If you can't wait for Apple to fix this, you could try reformating your system drive to case-insenstive HFS+ and restoring your ML install from backup. That fixed it for me. If you store your data on your system drive, check your files still have unique case-insenstive names first though.

How come Apple doesn't care about customer's voice now?

It's been over 3 months but they don't even give us a reply.