RaBiD

hi, i have a mz-n707. I havent done anything to it like hacks etc. When i record something on netmd it seems to work fine.. i can edit all the tracks etc. But then i take the cable out, then it plays normally. But the problem is when it goes into standby mode, then i press play it says blank disc when ive just recorded something on it about 30 seconds eariler. It hasnt always done this.. only recently but now it does it every time. Please help, thanks