OK, After some more tests, I noticed that if I disable acceleration with DRIConf, Amaya still work but is very slow, while it crashes when I disable DRI from the xorg.conf.
CC'ing Michel, as this information gives him a more precise idea about where the problem can be tracked down. Also, Michel, in a previous mail on this issue, you mentioned that it worked for you with the experimental versions of Mesa and X Server. I tried running the X server 1.1.99.901, and it still crashed. Any help is welcome, otherwise I will start to try sacrificing chickens. Regis