Topic: TASCAM DR1 creating a .wav file that is not supported

Hi folks,
My Tascam DR1 audio recorder has done something strange. When I got the end of my recording session, I found that the machine had switched off. Battery did not seem to be flat. When I switched it on, it came up with the message "Non-supported, Press Play". This refers to the last file created, or listened to. (Ie the file that is 'selected').  And indeed, the file that has been created, although it is just a .wav file, is not supported by Windows Media Player, with the following explanation that comes up when I try to open it in WMP: "Windows Media Player cannot play the file. The Player might not support the file type or might not support the codec that was used to compress the file." Strangely enough, the file has 0kb in it. I have a horrible feeling my recording is lost. That said, I need to prevent this happening again. What caused it? It is not doing it every time.
fingers crossed someone out there has a clue!
cheers, Kate