This morning I turned on my trusty Mac, just like I do every morning. And just like every morning, the desktop appeared and the apps I have set to automatically launch did their thing. By the time I sat down with coffee in hand, I was ready to get to work.
Or maybe not. After I warmed up my mouse (details here), I was ready to read my email, but when I moved the mouse, the cursor didn't respond. It was stuck in the upper left corner of the screen. I then noticed that the Bluetooth icon in the menu bar didn't show an active connection. Since my Magic Mouse uses Bluetooth, the menu icon should have shown an active state.
No problem. I'll just use the command+F2 keys to access the Apple menu, go to the Bluetooth menu item, and turn Bluetooth back on. That's when I discovered that the keyboard wasn't working, either. After some fiddling around, I discovered that all of the USB ports and the Bluetooth module in my Mac were dead. Well, nearly dead; the USB ports had power, but wouldn't respond to anything else.
I was a bit worried about the survival of my Mac Pro, but decided that the problem could just be its SMC (System Management Controller). This nifty piece of hardware controls many of a Mac's low-level hardware devices, including turning on the USB and Bluetooth ports. So, I set about performing an SMC reset, and what do you know; everything is working again.
I don't know what caused the SMC unit to behave as it did, but the reset took care of the problem. If you ever have a similar problem, and want to know more about the SMC and how to reset it, take a look at:
Resetting the SMC (System Management Controller) on Your Mac