PB's Airport Extreme card not staying connected - please help diagnose

Question

My thread Airport extremem card can't hang onto wifi signal - what to do? in the "Getting Online" forum hasn't generated a solution, so I'm trying here too.
In the past few weeks, my airport signal bounces around and randomly disconnects me. It goes from no signal (indicated) to 3 bars then bounces around. It occurred with my own Airport Extreme card (in the PB) and my Belkin router, and the library's wifi.
The problem may have started after an erase-and-install of Panther with an upgrade using the combo 10.3.9. The only security updates I see receipts or packages of are SecUpd2005-004Pan.pkg, SecUpd2007-002Pan.pkg, SecurityUpdate2004-10-27Pan.pkg.
The usual troubleshooting (Permissions, Chrons, Disk Warrior) didn't solve anything. Since first posting about this problem I've reapplied the 10.3.9 combo. I tried changing the channel on the router and setting it to Protected Mode.
"Protected Mode
NOTE: In most situations, best performance (throughput) is achieved with Protected Mode OFF. If you are operating in an environment with HEAVY 802.11b traffic or interference, best performance may be achieved with Protected Mode ON."
I then installed Airport 4.2 update because Software Updater presented it as an option.
Until today iStumbler and MacStumbler were showing 29-35% signal strength with no noise. As of today, iStumbler is showing intermittent noise of ~14-21%, but MacStumbler is not. (It was constant when I tried channel 9 and changing the router's back to 10 made it intermittent.)
The router is serving a desktop computer via ethernet so I can't move it. I have reset the router and cable modem several times with no improvement.
Does anyone have any ideas what I can do? Thanks.

Answer 1

I would have come back to edit this, to say that the dropping signal problem came back since the 10.3.9 combo but I couldn't. The darn wifi signal was lost for something like 7 minutes.
The PB was sitting in exactly the same place and toggling airport on and off wouldn't reconnect it. It generated many lines in the console. Anyone know what this means?
Aug 5 12:05:04 Marlinespikes-Computer kernel: AirPort: Link DOWN (AP deAuth 0)
Aug 5 12:05:04 Marlinespikes-Computer kernel: handleAirPortChangesChannelWL fails because POWER IS OFF (the mask is correcty set however)
Aug 5 12:05:13 Marlinespikes-Computer kernel: AirPort: Link DOWN (out-of-range 0)
Aug 5 12:05:13 Marlinespikes-Computer kernel: handleAirPortChangesChannelWL fails because POWER IS OFF (the mask is correcty set however)
Aug 5 12:05:17 Marlinespikes-Computer kernel: AirPort: Link DOWN (out-of-range 0)
Aug 5 12:05:17 Marlinespikes-Computer kernel: handleAirPortChangesChannelWL fails because POWER IS OFF (the mask is correcty set however)
2007-08-05 12:05:20.931 iStumbler[3432] WirelessCreateScanResults context:0x382A50 err: 0x88001003
2007-08-05 12:05:29.930 iStumbler[3432] WirelessCreateScanResults context:0x382A50 err: 0x88001003
2007-08-05 12:05:45.326 System Preferences[4011] connection:didFailWithError: can’t find host
Aug 5 12:05:53 Marlinespikes-Computer last message repeated 5 times
2007-08-05 12:05:56.930 iStumbler[3432] WirelessCreateScanResults context:0x382A50 err: 0x8800100B
2007-08-05 12:06:32.930 iStumbler[3432] WirelessCreateScanResults context:0x382A50 err: 0x8800100B
Aug 5 12:08:07 Marlinespikes-Computer last message repeated 14 times
: object: ./Applications/iTunes.app/Contents/MacOS/iTunes malformed object (inconsistant sizeofcmds field in mach header)
Aug 5 12:09:59 Marlinespikes-Computer last message repeated 8 times
Aug 5 12:11:55 Marlinespikes-Computer lookupd[3999]: NetInfo connection failed for server 127.0.0.1/local
Aug 5 12:11:56 Marlinespikes-Computer lookupd[3999]: NetInfo connection failed for server 127.0.0.1/local
Aug 5 12:11:56 Marlinespikes-Computer kernel: AirPort: Link Active: "belkinrouter" - 0011501e80e9 - chan 8
Aug 5 12:11:56 Marlinespikes-Computer kernel: handleAirPortChangesChannelWL fails because POWER IS OFF (the mask is correcty set however)
Aug 5 12:12:05 Marlinespikes-Computer configd[129]: SecKeychainFindGenericPassword err= -25308 ( =0xffff9d24) (current= belkinrouter)
(event handler):Can't find variable: autoSave
(event handler):Can't find variable: autoSave