i just bought a version 4 codebreaker to use to boot up my cdr backups. I tested at my friends house at first and it worked with his V4 no solder mod. I took it home and tried it on my ps2 using the knife method (using the same game as at my friend's house) and it didn't work. It took me back to the browser screen. any ideas.

That is interesting for the no solder only emulates the knife/cog swap... Should work fine.. Perhaps its a timing problem?
I have tried to swap using my codebreaker v4 and have only gotton a disk to shoot out at me spinning very fast.