I thought I had noticed my M1000 suddenly jumping to the beginning of a playlist and I finally have tracked down when and how it is happening.
I have a roughly 4000 song playlist that I usually shuffle play. The vast majority (99%) of the songs are WMA Lossless. I am using WMC for a server and I have the latest and greatest firmware running on the SB.
Here is what I see when it restarts the playlist:
While a song is playing (almost at the end), the SB starts buffering the next song which happens to be a WMA lossless with a bitrate less than 400K. So, the "Cannot play song xxxxx" message is displayed while the previous song is still playing. I didn't hit anything on the remote and after about 3 seconds the "Playback stopped" message is displayed. Again I didn't hit anything on the remote and after about 3 seconds the SB started playing the playlist from the beginning again.
I realize the lossless less than 400k bitrate issue is being addressed, but it would seem like this resetting to the start of the playlist is a different issue.