System seems to have crashed

MY philips DVDR520H seems to function ok, except one day when i turned it on and opened the browser window to playback something i had recorded, the pictures that indicate what has been recorded were all grey and after waiting a while to see whether they loaded they remained grey. when i try to play one of them, it freezes and i end up having to switch the whole thing off to get it started again. strange thing is that after this if i tape something its picture is displayed in the browser and i can play it no problem, but the ones taped before whatever happened remain grey and unwatchable. It seems if i deleted all the affected one my dvd player would continue functioning correctly, however i dont what to lose anything that i have on the harddrive. Is there anyway i can restore them?