A reminder: Errant USB devices can cause system freezes, other issues

Problematic USB devices can cause serious system issues, including repeated freezes, kernel panics and more.

Though this is an issue we've covered several times on MacFixIt, it appears there may be a new group of problems with USB devices connected to Intel-based Macs, as indicated by recent reader reports.

MacFixIt reader Cole Armstrong writes:

"My new Mac mini crashed on me within 24 hours. I did not change any of the stock settings or add any new hardware to the box itself. It was to the point that I could not even re-install the OS. Before it would boot the OS I would get a multiple languages message saying I needed to restart. Every time I booted up and I never got to the OS.

"Apple Tech support could not help me with the matter. So I had to send it back. I received my second mini in the mail a week later. Same configuration: 1.66ghz Core Duo/80gb HD/2gb's RAM. 24 hours later it then crashed...luckily I was able to reinstall the OS, I changed from my brand new OS X compatible Microsoft Keyboard, and bought an Apple Brand Keyboard.

"So, I re-installed the OS without the Microsoft keyboard plugged in. Then I used the Apple Keyboard to complete the install.

"So far my system runs very quickly and smoothly and I am not having running midi programs. The whole system just seems to run a lot better and I get that gut feeling that it is fixed. I have been up and running now for 36 hours with no problems....this is a new record."

If you are experiencing an issue like this, you may also find (using the Activity Monitor, located in Applications/Utilities) that the process kernel_task exhibits inordinately high processor usage.

Aside from the obvious solution of simply disconnecting the offending USB device, you may want to try resetting NVRAM via the following process: Hold down the Command, Option, O and F keys at startup. When the prompt appears, type:

• reset-nvram (then press return)
• reset-all (then press return)

You may also want to doing a deep clean of system caches with a tool like Cocktail or Tiger Cache Cleaner. Doing so has been known to restore connectivity with, and eliminate problems caused by problematic USB devices and potentially corrupt kernel extension caches.

Feedback? Late-breakers@macfixit.com.

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