This was caused by working (editing, recording and playing) in AudioVision with audio and/or video drives almost full. The problem was resolved by copying data from one drive to another to free up space, but in the process AudioVision lost the last version of the sequence which was a loss of several hours of work.All drives (i.e. the internal OS drive, as well as the external audio and video drives) should not be filled to more than 90% capacity. Once a drive only has 10% of free space, immediately back it up, initialize it and restore only the needed data.