Maybe it's your PS2 version, since models after v5/v6 have extra copy protection crap in their BIOS. What version is your PS2? I've done this method on a v5 (really the best PS2 model) and it worked perfectly. The v5/v6s are the 3000xR (this last number will vary depending on your region, e.g. 0 if in Japan, 1 in the Americas, 2 in Australasia, 3 in the UK and 4 in the rest of Europe.) models.