Playback freezes then forces reset with USB-connected drive

I have two of these WD TV Live boxes. I updated one of them to the latest firmware and then started experiencing freezes after about an hour of watching one or more shows. This is with a USB-connect external hard disc drive on its own power supply.

At some random point in a random mkv file, everything would be fine when the picture suddenly freezes and after about two-four seconds (not sure how long), everything goes blank. I have to reset the box in order to watch the same file, using the scan forward to reach where the system froze.

This started happening after I updated to the latest firmware. I swapped out boxes and with the box with the older firmware, everything is playing back fine with no freezes.

I have made sure the files are all defragmented, but that doesn’t seem to change anything. This is very frustrating. Any ideas what happened? Or how to reinstall the updated firmware? I turned the firmware updates off for the box with the older version, simply because I don’t want it to do the same thing to me.

Possibly the device is overheating?