I am noticing the same behavior on my system (using iwl3945 on a
Thinkpad T60p with the Intel 3945ABG card). That includes the "0
packets captured" on the interface during DHCP request. However, I
noticed that if I run `ifconfig wlan0 up` before running `ifup wlan0`
it seems to resolve the problem and the computer receives a DHCP
response from my DHCP server with no problems. It may be related to
the fact that settings applied with iwconfig do not appear to stick
unless the interface is up.
I would be interested to hear if this makes a difference on any other
systems...