Ever since I got my 17-inch G4 iMac in December 2003, I’ve periodically run into a problem where the computer would lock up when entering sleep mode: the screen would be dark, but the computer would not respond to any user input. It happened relatively infrequently, and relatively irregularly: a couple of times a week, then nothing for months. One suggestion was faulty RAM, but I didn’t think that fit the description. At least it was infrequent enough that it didn’t interfere overmuch with my work; I rarely, if ever, lost any data.

It happened again this morning. For some reason it occurred to me to yank out the Bluetooth adapter from the USB hub. It worked immediately: the computer sprung back to life.

Now why didn’t I think of that before? That Bluetooth adapter — it’s an older D-Link dongle that isn’t compatible with Apple’s wireless mouse and keyboard — had been giving me trouble with my G3 iBook. Just not the same kind of trouble, I suppose, or I’d have recognized it sooner.