OK, you need to get iwconfig to set the configuration before any DHCP request will work.
when i run iwconfig sometimes it shows the access point address that i designate
This statement bothers me a lot mainly because you talk about an access point address. You don't use iwconfig to connect to a specific address, rather you use it to connect to a named access point. Rather than guessing, if you could post the commands you use to configure your card it might help.