Quote Originally Posted by Caravel View Post
I would bet on overheating. Most drives have a thermal cut out that will cause them to power down to prevent damage to the disk platens. You probably wouldn't have heard the drive powering down because a) WD drives are usually very quiet and b) you have a second drive which would drown the sound of the other one out anyway. I have had drives that failed that could be got working again for long enough to back up the data. Putting the drive in the freezer was another old trick (don't try that one).

How is your case ventilation? (Bear in mind that the weather is warmer here lately).
Now that is a very good thought. I have a tsunami dream case which has vents at the front as well as at the back and some nice big fans and good heat dispersal overall. The weather here has been baking, the hottest it's been in several years. Yesterday I'd been using the PC for a few hours before it started playing up, and the first time I'd been writing for an entire afternoon.

I shall have a wander into the temp monitoring page in the machine's set up ...