PS2 not playing backups

[Beryltheperil]

Hi, don't know if ne1 can help. I've got a v3 PS2, with an original Messiah chip in it. It was fitted about a year and a half ago, and I've had no problems. Suddenly, its stopped playing back-up cd's although its still playing backup DVD's.

NE1 know if there's a way around this, or do I need a Messiah 2??

Thanks
Bezza