I have Matshita DVD-RAM UJ-820S drive fitted in Acer laptop. 15-20 mins into playing a DVD the drive speed reduces & sounds as though disc is fouling something inside. After re-starting this problem happens with increased regularity although better if I let it cool down for several minutes. Is it something to do with labels I'm using I wonder. Same DVD's (DVD+R) play fine on other drives. Any suggestions?