All CDs - Disc Read Error

[spudlet]

I have recently modded my V4 PS2 with a no-solder chip. Immediately after I tested the machine to see if it would play legal DVDs and CDs. Which it did. I have now been using the swap method to boot DVD+Rs for about 4 days and they have worked perfectly so far. However, the PS2 now refuses to recognise all CDs - PSX, music and even legal PS2 CDs such as Pro Evolution. I've not even tested a CD-R game yet as I have been umable to boot the Swap Magic CD. As I said, initially I was able to boot Pro Evo but it refuses to now- gives a Disc Read Error after alot of whirring and clunking.

Anybody experienced this and/or have any ideas where to proceed with this?

Best Regards,
Andrew.