ps2 not reading dvd's but plays cdr's

[matt1]

I have a ps2 v4 with a neo4 chip. I am going to upgrade my chip to a messiah 2, but only recently have found that my ps2 isn't reading any of my original dvd games or movies. It does however play backup cdr games. I have replaced my laser about 18 months ago but have only been playing original dvd games and movies since. What is the problem????? Can anyone help????