Matshita DVD RAM UJ-8A0AS ATA Device problems

MY DVD-RAM UJ8A0AS DOES NOT BURN ANYMORE, WHEN I INSERT A DISK IT TELLS ME TO ADD FILES TO COPY BUT WHEN I DO THAT AND TRY TO BURN. THE WARNING BOX THAT TELLS ME THAT THE SPEED FOR BURNING IS NOT RIGHT PPOPS UP AND TELLS ME TO TRY AGAIN. EVEN IF I TRY TO CHANGE THE DISK NOTHING CHANGES THE SAME BOX POPS UP.