Tried a lot of combinations, and finally found the right solution, I think.
First dlink and airport wanted to be both dhcp and conflicts were welcome.
Then I deactivated the one of dlink, given the airport 192.168.1.2, but when distributing Ip(dhcp&nat) it wasn't possible with static ip's so other option range: 192.168.1.3-.1.200. But deconnections found place and I still don't understand why. Then tried to dlink dhcp and airport not. But the airport cannot act as a bridge, he WANTS an Ip, so again sometimes internet, sometimes not. meanwhile, the computers had a manual adress using dhcp. then tried dlink to give a range from .1.1 to .1.2 and airport .1.3 to .1.200 worked fine for half a day(DHCP only). Tried last with DHCP&NAT but the airport takes ip 192.168.1.1 and conflict with modem.
Last one I tried, and I had to do it first. The dsl act as a bridge and the airport enters login information to the modem to connect and dhcp/nat. for the moment, It works fine for a week already, but still waiting...
And their, the dsl acts as a real bridge, it asks no ip, nothing, so that was the best solution.
Hope it helped
If it can help my belgian friends, its for the full adsl connection