IItonics 256m -Over Record what does it mean?

Hi,

I mainly use this Mp3 device for recording lectures. In the last month or so the screen some times read OVER RECORD . To day when I used it saving along the way on shutting down /saving it just went back to Rec1 and now reads OVER RECORD (?), before when this happen I used the PC to default set it. The information that I was recording today is really important, so I don't want to reset in this way. when I open the mp3 player from the PC it says that there no files.

Can someone please explain to me why its happened and is there anything that I can to gain access if possible to my recordings.

Thanks in advance

Nick