My Rez copy did the same thing, but on the newer PS2, I messed with it for an hour, but kept getting "read disk error".
I was pissed cause I had my original PS2 apart for repairs.
3 month later, I tried it again on the newer PS2, this time it loaded fine, I didn't do anything to the PS2 or the disk.
I'm at a loss to why it worked that time and not the last.
It still works fine.