Mac mini restarts randomly and sometimes throws power-down error

I have a (2H) 2010 Mac Mini model that keeps restarting itself at random times.

The frequency of the restarts are probably 2-3 times a week. I'll return to my desk and am treated to the main login screen, where I have to login and all my programs have to be relaunched.

Occasionally, I even get a weird error message that overlays over the entire screen... "You need to restart your computer. Hold down the power button until it turns off, then press the power button again"



I thought this may have been a cooling problem, so I got a USB fan and have it cooling the CPU. Even now, after I restart I feel for heat and the mac mini is very cool, not hot.

The mac shows a problem report after restart...
You shut down the computer because of a problem.
"thread_invoke: preemption_level -1, possible cause: unlocking an unlocked mutex or spinlock"

Has anyone had this issue or have any suggestions?

That is a Kernel Panic. One question, have you added any Memory (RAM) since you purchased it?

Yes, I've swapped out original RAM with two 4GB slabs, making it 8GB total.

I bought these...
Amazon.com: Crucial Technology CT51264BC1067 4 GB 204-pin SODIMM DDR3 PC3-8500 CL=7 Unbuffered NON-ECC DDR3-1066 1.5V 512Meg x 64 Memory: Electronics

Since your crashes are frequent enough, replace the Crucial memory with the original memory that came with the Mac Mini and observe for a few days to see if it's stable. If it is, then Crucial memory you got is either the cause for the crash or you didn't seat it properly..

OK. Is it common for memory to be bad?

Is this typical of Crucial Memory? Should I look to get a replacement brand / type if this is the cause?

Crucial is normally some of the best RAM out there. If the old ram solves the Panic, then you either got unlucky and got a bad stick or as Razor said, maybe one stick is not seated all the way.

RAM chips are sensitive devices that need to be handled properly as far as ESD is concerned, the newer RAM chips are way more ressilient than the older ones, but it is still possible to cause damage. Name brand chips like Crucial are usually all tested before they leave the factory, so a fault with the manufacture process is not likely. Not seating the RAM properly however can potentially cause problems with a lack of proper ground and other things..

So run the quick test by going back to the original RAM ensuring that you are safe with it's handling (i.e., discharge yourself on a piece of metal before holding the RAM) and ensure that the stick is inserted fully and securely and let us know how you fare..

Well, reporting back (sorry it takes a while for the problem to manifest).

So here's what I now know...

1. I don't have the original memory anymore. So I just opened up the mac mini, and checked to see if the memory looked properly seated.

I did notice one of the plastic clamps on bottom memory was bent, and after trying to straighten it, it broke off. Here's a pic...



pointing to the bent plastic clip and metal surround. circled the plastic part that broke off.

2. I tried booting with just the bottom memory attached (the one with broken plastic clamp) and I eventually got same error after about 4 days.

I can try again with the other memory to be sure its bottom only. But I think it likely is the clamp is the issue vs. the memory.

Mac mini is less than 1 year old, will apple store support a warranty fix this?

Considering the RAM is user serviceable and the break occurred while installing RAM - when I was a technician, I would have covered it. Talk to a technician, let them know what happened, and ask if it can be covered. My guess is that it'll be no problem.