System Freeze. Cursor moves but adds horizontal lines. Mountain Lion.

A few suggestions, stop if one of the procedures solves the issue.

1. Repair HDD Permissions
2. Reset SMC
3. Reset PRAM and NVRAM

Also you may want to run a full hardware diagnostic test in order to see if your Mac is experiencing some type of hardware failure. I suspect the Apple AHT test is available on your Mac either by holding the "D" key on start up or by inserting the Applications Install DVD that came with your Mac into the drive and reboot your Mac while holding the "D" key.

For more information about the AHT visit this article.

http://support.apple.com/kb/HT1509

Did you tried running the Apple AHT from the Applications Install DVD that came with your Mac? Let me know...

Richard Jackman wrote:

No Install DVD available.

Well, your best bet in order to run a hardware test is to go to an Apple Store Genius Bar and set up an appointment.

Visit:

http://www.apple.com/retail/geniusbar

Alternatively you can check your computer at the nearest Apple Authorized Service Provider.

Having the very same issue here. Late 2009 iMac 27" 2.8GHz i7 (10.8.2).

Tried a host of tests (as suggested above), but can only boot into safe mode.

My iMac qualifies for the replacement hard drive and I had just (last Thursday evening) purchased a Seagate usb external drive and cloned the drive to it. Come Friday evening, I booted from this USB drive to check all was working - and all looked fine, until after the computer went to sleep. When I attempted to wake the computer, it wouldn't respond. After a hard restart, I'm suffering the same issues as Richard.

No luck booting to the Recovery partition and can't boot to the new USB now either.

At least I have Time Machine and Carbon Copy Cloner to hopefully recover from after the hard drive gets replaced. I'll have to do it now - and not wait any longer.

Mine too. Was convinced from internet search this was a hardware issue. Possibly logic board or graphics adapter. Did all the usual resets and hardware tests.

Turns out, (so far so good) that emptying the internet plugin folder and reinstalling Java and Flash has cured the problem.

Good luck.

Just got the same issue with my iMac Late 2009 model last night. Was running Lion and upgrading to Maverick didn't fix it like I was hoping it would.

Hi,

Just expering the same problem on also a late 2009 iMac. I performed an AHT cause I have the dvd. But no problems detected. Any of you guys got a solution yet?

Regards

Erik

Hi,

After doing all above tips I still had the problem. Unplugging it for a few minutes did not help, but after 12hours unplugged it started up just back normal.

Hopefully this can help other users.

Regards

Erik

It a dying graphics adapter. It needs replacing. Any cure, re-boot, memory clean, re-set etc etc will only be a tempory fix.

You're right, after 2hours of working I got the same problem again.

Thx for the reply.

Erik

Sorry about that. Cost me £200 to swap with Apple or a third party will upgrade the part as well for the same money.

After it's done you may wish to download SSD Fan Control to control a cooler point where the fan kicks in.

Good luck.

My problem finally got fixed - It appeared to be the graphics card, but in the process of swapping out, the mother board failed. So a 2nd swapped out graphics cards, new mother board and all appeared to be finally fixed. I'm so glad this all happened while at a repair centre. Apple helped enourmously!! Much cudos to them.

Graphics card is replaced and everything seems to work. Will definitly try the Fan control software!