Was the mic you were using battery powered ? My mic has a small battery in it which you can switch on. The problem is that when the battery runs out the mic stops recording - however if you switch the mic OFF, it takes its power from the MD unit and continues to work! It took me a while to figure out that this was the case and ended up with a couple of blank recordings of great sessions. If this was the case however the disk itself would continue to 'think' it was recording, so the timer etc would still be running.