DMC3 on PS3

[Reapz]

So DMC4 is released soon and I never got round to beating DMC3 so I restarted it a few days ago on my PS3. I am on mission 18 now at the part where you fight all the bosses again, but clicking circle at the light blue(Cerberus), yellow(Gigapede) and purple(Nevan) stones does nothing, which is a bit of a problem because I need to fight Cerb to progress :/
Any ideas? It doesn't make sense why those certain 3 stones don't work but all the others are fine, I hope it is just me making a retarded mistake, game was getting good

[Kazen]

Try cleaning the disc, it could be a piece of dust that you cant see in it. I've had that with games before on the ps1/ps2 where cleaning the disc would stop the problem.

[Exoduso]

I can't seem to find the DMCs anywhere, I want to replay them before 4 comes out.. ;;

[Reapz]

You can all stop worrying now, it worked fine when I tried again yesterday and I have completed it ready for DMC4! Delete plez