Thanks a lot for replying.
I found the string in 1st_read.bin, so I'm going to make a modified copy as you said. I only have a 56k connection and I spend a lot of time downloading a game, so I really want to get it to work !
However, if it's not the patch, what could it be in your opinion ? I thought it may be a PAL protection, but Pal Patcher can't find any and I didn't find any patch for this game... So I don't know what's going on, and your solution is my last hope