Matt, Thanks for posting.
I neglected to post a play-by-play of what exactly was occurring as I created the log file because I wasn't sure anybody was going to help, but the sequence of events is roughly:
1) Reset Playback to WASAPI, 24 bit, 2 ch, 44.1kHz.
2) Turn on logging
3) Start playing a track (it isn't really SACD, it's just a rip of the redbook layer, simply a *.wav file)
4) Track played for about 2 min 33 sec (approx.) and then something caused it to stop (sound and visual waveform on the header both stopped); I was using standard mode, not Theater Mode;
5) I noticed the Pause/Play icon was still displaying the option to Pause (i.e. the player did not even recognize it had stopped playing!) so I tried to Pause the track;
6) Pause had no effect other than to change the icon to show the option to Play (Resume) [i.e. the forward arrow similar to this: |>];
7) Finally hit Stop - which amazingly enough did shut off the player;
8) Again hit play for the same track, it played about 2 min 20 sec this time and the again stalled, repeated the Pause/Play/Pause/Play/Stop sequence as described above;
9) Tried a third time, same track, I think it played about 30 seconds, repeated Pause/Play/Pause/Play/Stop nonsense;
10) Tried a new track, same thing, can't remember how long it played before stopping,
11) Tried another new track, etc.
12) Gave up. Terminated log. Sent log.
Took rig into house. Got pissed, disconnected HDD from one port on the 4-port USB2 hub and connected it to a different port. The Dragonfly DAC remained connected to the same hub port. I left the Dragonfly output dongle disconnected. Lo' and behold! I came back an hour later and the thing was still going (the waveform on the track header was dancing around instead of dead in the water.) Stopped playback, changed albums, and resumed play. It continued to work for a couple of hours.
I did encounter a drive disconnect when I put the computer in Standby or Sleep for a few hours. When I restarted the computer I had to physically disconnect the HDD and reconnect before the computer would recognize the HDD again (obviously not JRiver's issue.)
I tried decoding the logfile by trying to recall the logfile event sequence from my own memory, but I cannot see anything in the log that tells me why JRiver lost track of the HDD. Windows 8 Event Viewer also provides no information regarding loss of HDD connection/communication with my computer (which I am fairly amazed by - normally Windows tracks events very well.)
I am not 100% convinced the problem is gone, but I'm fairly sure it is my computer/HDD that is the problem.