So, to sum up, I can boot into Leopard only in framebuffer mode and ONLY if I leave the Geforce/nvidia related kexts alone. If I insert only my dev id, the system won't boot at all anymore, although it should... Needless to say, the specific dev id is NOT present in the info.plist of the unmodified kexts. It's a bit confusing, to say the least, I mean the card only works when its specific entry is NOT present in the list...