Primus

Hi, Can anyone help me? I have a SONY MZ-G750 which will play MD's fine but when I go to record it keeps telling me MEM OVER! When I look this up it tells me "You tried torecord with the recorder placed where it receives continuous vibration" Thing is that I have it lying on my loounge floor with no vibration at all! I have tried two or three new MD's and still the same message. Any help would be grateful.