[JCheyne]

At my office, I have an AirPort Base Station (V5.5) hooked up to the office network. My printer plugs into the AirPort via ethernet. I bring a PowerBook (1GHz, 17"; OSX 10.3.8) to work and it automatically connects to the AirPort - or at least is should. Every once in a while, the AirPort icon in the menubar is nothing but grey.
I've set up a closed network with 128 bit WEP encryption, so here are the solutions I try to get the PowerBook and Base Station on speaking terms again:
1) Select "Other" from the AirPort menu, enter the network name and password. Result: "There was an error in joining the network blah, blah."
2) Reset the AirPort Base Station. Result: AirPort is still greyed out, and step #1 still doesn't work.
3) Restart the PowerBook. Result: Same as #2.
4) Repair permissions with Disk Utility. Result: Same as #2.
5) Restart after repairing permissions. Result: AirPort is back in black, and ready to go.
This happens most frequently when I've first come into the office and first tried to access AirPort, but it has also happened in the middle of the day after I've already accesssed the network (Printer, email, Internet) via AirPort.
One other piece of info: At home, I use this same PowerBook and access the Internet wirelessly through an AirPort card I've installed in a G4 400Mz Mac that is attached to the cable modem. So far, I have not found this problem there.
Any thoughts on what could be causing this, and what solution is available? Is it a wakeup from sleep problem? I cannot positively recall at what point in updating software this first happened, but I have installed all of the most recent updates for my hardware & software setup, and I regularly run scripts (via Onyx) and maintenance (via TechTool Pro 4.0.3) to keep things running smoothly.

[HMB]

I take it you put your Mac to sleep before leaving for work, then wake it up when you get in to work? If so, try turning off the Airport card before you put it to sleep (from the MacOS Airport menu item), then turn Airport back on again after waking the Mac from sleep.

[JCheyne]

This solution - turning the AirPort off before putting the computer to sleep - offers a solution. Thanks. And if I forget to do it, the reliable fix is to turn AirPort off, restart, and turn AirPort back on.
But this is a software glitch, right? Anyway to fix the problem (from the user's side, not Apple's)? At work, it's a bit annoying either to turn AirPort off everytime I leave my office, or to set the computer so that it never sleeps.
Is there something buried in one of those mysterious OSX "leave me alone or else" folders that has gotten corrupted or that can otherwise be addressed by mere mortals?

[HMB]

Yes this is a "software glitch". It is also a very common problem posted in Apple's own discussion forums - where I have yet to see a definitive solution to this problem posted. My unscientific speculation is that the MacOS software installation (as it pertains to Airport wireless networking) on some people's Macs is "not quite right" - otherwise I cannot explain why this happens to some people but not others despite all known user-configurable settings being correct. Would a reinstall of the MacOS solve the problem? I don't know for certain.

[JCheyne]

The problem is back - big time. I came into the office (after a week's vacation) and noticed that the AirPort signal in my PowerBook menu bar was greyed out - no AirPort signal.
I went through the usual routine: Is the Base Station on? Yes. Does it show a signal? Yes. Tried turning off AirPort on my PB, restarted, turned AirPort back on. Still grey. Tried resetting the Base Station (Extreme, by the way). No luck. Tried unpluggin the Base Station (for about half an hour). No luck.
Then, as I'm minding my own business, suddenly the signal is there and a dialog box is asking if I want to join the network, etc.
A few moment later, though, the AirPort signal greyed out again, and it's been that way since. No magical sequence of repairing permissions, resetting the Base Station, unplugging and replugging the Base Station, Restarting the computer, or anything else I can think of, has worked.
NEWS FLASH
So as I'm typing this forum entry to find an answer to this problem, suddenly the default AirPort network appears, and I'm all set to go. I had to go back into AirPort Admin Utility and reconfigure everything, but it seems to be fine now.
Is there some sort of time-out mode that locks up the Base Station if it hasn't been accessed in a long time? Why was I able to get the signal back for a few moments earlier today? Is my Base Station schizophrenic, or otherwise on the fritz? (I do not suspect damage, since it is not moved anywhere at all. It stays connected to the business network 24/7, but I've created a closed network, so I doubt that it's been fiddled with.
Entirely frustrating, especially when trying to accomplish time critical work. If anyone can suggest a reliable fix, I would be grateful.