[ltp] T42 wireless problem - DCHPDiscover for wlan0 finds nothing.

[Tim Ottinger]

I'm running a Thinkpad T42, using the built-in wireless radio, running 
Debian
Etch.  I update my machine pretty frequently, probably twice a week or more.
I have never had any trouble with Linux wireless until recently. 

I'm a programmer, and use Linux on all my machines, but I'm not a very 
skilled
sysadmin, especially networking.  I'm especially nooby with wireless 
networking.

lspci says my system has:
    0000:00:00.0 Host bridge: Intel Corporation 82855PM Processor to I/O 
Controller (rev 03)
    0000:00:01.0 PCI bridge: Intel Corporation 82855PM Processor to AGP 
Controller (rev 03)
    0000:00:1d.0 USB Controller: Intel Corporation 82801DB/DBL/DBM 
(ICH4/ICH4-L/ICH4-M) USB UHCI Controller #1 (rev 01)
    0000:00:1d.1 USB Controller: Intel Corporation 82801DB/DBL/DBM 
(ICH4/ICH4-L/ICH4-M) USB UHCI Controller #2 (rev 01)
    0000:00:1d.2 USB Controller: Intel Corporation 82801DB/DBL/DBM 
(ICH4/ICH4-L/ICH4-M) USB UHCI Controller #3 (rev 01)
    0000:00:1d.7 USB Controller: Intel Corporation 82801DB/DBM 
(ICH4/ICH4-M) USB2 EHCI Controller (rev 01)
    0000:00:1e.0 PCI bridge: Intel Corporation 82801 Mobile PCI Bridge 
(rev 81)
    0000:00:1f.0 ISA bridge: Intel Corporation 82801DBM (ICH4-M) LPC 
Interface Bridge (rev 01)
    0000:00:1f.1 IDE interface: Intel Corporation 82801DBM (ICH4-M) IDE 
Controller (rev 01)
    0000:00:1f.3 SMBus: Intel Corporation 82801DB/DBL/DBM 
(ICH4/ICH4-L/ICH4-M) SMBus Controller (rev 01)
    0000:00:1f.5 Multimedia audio controller: Intel Corporation 
82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) AC'97 Audio Controller (rev 01)
    0000:00:1f.6 Modem: Intel Corporation 82801DB/DBL/DBM 
(ICH4/ICH4-L/ICH4-M) AC'97 Modem Controller (rev 01)
    0000:01:00.0 VGA compatible controller: ATI Technologies Inc M10 NT 
[FireGL Mobility T2] (rev 80)
    0000:02:00.0 CardBus bridge: Texas Instruments PCI4520 PC card 
Cardbus Controller (rev 01)
    0000:02:00.1 CardBus bridge: Texas Instruments PCI4520 PC card 
Cardbus Controller (rev 01)
    0000:02:01.0 Ethernet controller: Intel Corporation 82540EP Gigabit 
Ethernet Controller (Mobile) (rev 03)
    0000:02:02.0 Ethernet controller: Atheros Communications, Inc. 
AR5212 802.11abg NIC (rev 01)

And uname says:
    Linux toucan 2.6.15.1.emp7 #1 PREEMPT Thu Feb 23 15:11:43 EST 2006 
i686 GNU/Linux

You can see I'm running the EmperorLinux kernel.  I've not changed 
kernels, and this has worked for be until now.
Maybe I need to?  Anyway:


Current state of my problem is that I can't connect to wireless access 
points.
I can "iwconfig", and I can "iwlist ap" just fine.

 > sudo iwlist wlan0 ap
    lo        Interface doesn't have a list of Peers/Access-Points
    eth0      Interface doesn't have a list of Peers/Access-Points   
    wlan0     Peers/Access-Points in range:
        02:12:F0:02:12:AF : Quality=18/94  Signal level=-77 dBm  Noise 
level=-95 dBm   
        02:12:F0:02:12:AF : Quality=17/94  Signal level=-78 dBm  Noise 
level=-95 dBm   
        02:12:F0:02:12:AF : Quality=15/94  Signal level=-80 dBm  Noise 
level=-95 dBm
    sit0      Interface doesn't have a list of Peers/Access-Points

However:

 > $ ifup wlan0
    Internet Software Consortium DHCP Client 2.0pl5
    Copyright 1995, 1996, 1997, 1998, 1999 The Internet Software Consortium.
    All rights reserved.

    Please contribute if you find this software useful.
    For info, please visit http://www.isc.org/dhcp-contrib.html

    sit0: unknown hardware address type 776
    sit0: unknown hardware address type 776
    Listening on LPF/wlan0/00:05:4e:51:2f:64
    Sending on   LPF/wlan0/00:05:4e:51:2f:64
    Sending on   Socket/fallback/fallback-net
    DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 5
    DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 6
    DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 10
    DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 13
    DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 14
    DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 8
    DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 4
    No DHCPOFFERS received.
    No working leases in persistent database.

    Exiting.

    Failed to bring up wlan0.

Up until sometime last week (sigh -- I don't know the event) it worked 
just fine.
I would love some information about how to debug this, or how to fix it. 

Now this is the consistent result.  I'm stuck using windows for 
wireless  connectivity
which saddens me.