How can I make a working Silpheed PAL back up?

Hi from Spain,

So far I've been able to make working back ups of 5 PAL games: Tekken Tag, Moto GP, Kengo, Star Wars and Gun Griffon; without any patch, just making straight copies with clone cd or nero.

However, today I've burnt 3 PAL Silpheed, and the copy is succesful but it just doesn't work in my PS2. Do I need a patch? Must I do something special?

In general, can most PAL games be copied without the use of any patch, as I made the other copies?

Thanks for your help