Orig. Airport card loses IP, maintains connection to Linksys network

Question

I'm posting here because I don't see a listing for plain old Airport cards. If there's a better spot in the forums for this, please let me know where it ought to go.
The setup:
Dual 867 Power Mac G4 (MDD) with old-school Airport card (both purchased back in 2002), running 10.4.10, and connecting to a Linksys wireless network (WRT54G wireless G-router, with a WRE54G wireless-G range expander). For the most part, this has worked out very well for the past several months.
The problem:
The IP address seems to drop out randomly, but not the wireless connection itself. I'll lose internet access, but have a full four bars on the Airport signal indicator. Pinging either the router or the extender fails. Shutting off Airport via the menu bar and then turning it back on will bring back the IP.
The bigger problem:
This used to happen once in a while, now once or twice a week, but switching the Airport off and then on brought it back. Now it's happening every five to ten minutes, starting this evening. It does it with both static and dynamic IP addresses; the static IP remains in the System Preferences window, the dynamic one actually vanishes until I restart the Airport card.
I ran into wireless problems yesterday where the SSID and the network just up and vanished. I'd previously attributed this to environmental considerations since it had happened a few times before and normally fixed itself within 30 minutes to a few hours. After it failed to come back by this morning I upgraded the firmware on both the router and extender to the latest versions available from Linksys. All was right with the world for several hours.
Until the problem with the IP dropping while the wireless connection remains returned. Then it got worse. Now it drops on a far more frequent basis than before. This only happens on my desktop Mac. I'm on my Windows XP machine (same room, same wireless network, using a Linksys USB wireless adapter). The Windows machine is fine; it does not lose IP address when the Mac does. Since I have a full connection and the Windows machine doesn't seem bothered at all, I'm guessing it's something to do with the Airport card in the Mac.
Apple's software update tells me there's no new software available for my machine, which leaves me with no idea what's causing this or how to fix it.
Any advice, solutions, or tips are greatly appreciated.
Thanks!

Answer 1

Some of this might be review for you...
An IP address is how the data finds you on your respective network, like the street address on your house. When you boot up your computer and connect to your network your computer is connecting with either a static or dynamic IP address. Static means every time you boot up, your machine is using the same one you've assigned to it. Dynamic means that each time you boot up your machine gets whatever one is next in line.
Odds are if you've never set this, you're using a dynamic address which means you're using DHCP. To check, go to your System Preferences -> Network Preferences -> and double click on the Airport connection. You'll see a few different options, so click on TCP/IP. That will show you if you've got a static IP address ("Manually" appears on the pull-down menu) or a dynamic one (DHCP).
Unless you have to forward ports or are looking for volumes on your network using a static IP, DHCP for a dynamic IP is fine.
The "new" Airport card wasn't a 100% fix. My IP address does seem to mean nothing every once in a while. I sometimes have to switch the Airport off and then turn it back on. Since toward the end, my old Airport card stopped seeing the wireless network entirely, even when my XP box saw it clearly, replacing the card was still a good idea for me.
Good luck!