Turning off Wi-Fi crashes computer!

I have a 2008 MacBook Pro running Mavericks, that is giving me fits.

I have wi-fi turned on all the time. I could turn it off, but I dare not, because if I do, within a few minutes the laptop crashes so hard I can only turn it off; the power button's the only thing left working. When it's in that state, it will not make it through an entire restart, even in safe mode.

To fix it, I have to start up into the recovery partition, then use the Terminal app to delete or replace the folder /Volumes/Macintosh HD/Library/Preferences/SystemConfiguration . That fixes it, but unfortunately it leaves Wi-Fi turned on. I want to be able to turn it off.

I've tested where I copy the existing SystemConfiguration (when Wi-Fi is turned on), turn Wi-Fi off, give the computer a minute for a really good, solid seizure (and sadly, it did not disappoint), and then replace the SystemConfiguration folder with the copy. It came up again, all smiles as if nothing happened, Wi-Fi turned on as always.

And yes, I have deleted the SystemConfiguration folder and let the system rebuild it on restart. It does that just fine. When it rebuilds, it leaves the Wi-Fi turned on, and it still has exactly the same problem: Next time I turn Wi-Fi off, it's poleaxed-steer time.

How do I fix this so I can actually turn Wi-Fi off? For that matter, how do I troubleshoot this to find the cause?