PSU-PS2: Cannot enter certain mission areas?

[Aarokh]

I have a problem with my PS2 version of PSU:
Whenever I try to enter missions in moatoob (valley of carnage), or the 4th block in the second linear line mission, my PS2 stops loading and it just idles until I get a disconnect error. I bet there are more missions that probably won't load for me but those are the ones I figured out while trying out my PS2 version yesterday. The CD has some small scratches but the game itself doesn't crash from not being able to load.. in fact the CD doesn't rotate at all when i open my slimline PS2 lid.

So: did anyone else have the same or similar problems with certain missions? Is this because of the CD and I should bring back the 2nd hand copy to the store and buy a brandnew CD? Or might this be a router setup issue and I just forgot to forward certain ports or something when setting up my PS2 for network?

Everything runs fine on the PC and I can enter any mission. It's just the Ps2 that disconnects me in certain areas.

[SabZero]

Could be a disk error. Write to sega for a replacement, they might just help you out.

[rena-ko]

any scratches on the disk? if yes, try sega. if that doesnt work, try this disk repair tools.

[Aarokh]

It was a CD error. TY for the responses. Everything seems to work now with a fresh CD.