Airport Problem: Self assigned IP address?

I'm using DSL, I've had it for about 4 weeks. For the past week or so I've been having a problem connecting to the internet wirelessly through airport after the computer goes to sleep and is rewoken(rewaken?). I get this message when i go to see the network status in the system preferences:

"Airport is connected to the network Sundance. Airport has a self assigned IP address and may not be able to connect to the internet."

For the first three weeks i NEVER had this problem, and now it shows at least once a day. I figure i might have changed something in my network preferences but i don't know what. I don't really know what dhcp or ipv6 or ipv4 is but it is set to "using dhcp" under the tcp/icp menu in the configure ipv4 section and configure ipv6 is off.

sometimes if i turn airport off for a few minutes and then on again the internet will work, sometimes if i don't turn it off it will work after a few minutes...???

oh by the way, the pc i use that is also on wireless doesn't have this problem.

any help would be great!

HI,
If your DSL modem is plugged into the normal ports behide the router then DHCP will not work, U have turn it off and enter the IP's you got with your connection.

i have this same problem, could you be a little more specific on how to solve it? my network preferences also go crazy each time I open it saying the settings have been changed by another program. Is there any way to reset it?