All devices working with AEBS except one

Question

So I have a network with an Airport Extreme Base Station. Several devices use the network without any problems, including:
MacBook Pro (older Core Duo model) - running OS 10.5.8
Powerbook G4 (still kicking) - running OS 10.5.8
Mac Mini (new, Core 2 Duo) - running OS 10.6.x
iPod Touch
iPad
The AEBS is set to use DHCP, and all machines seem to be functioning fine with the network, despite various processors and OS versions. The Mini is a server that is left running 24/7, while the others connect and disconnect to the network throughout the day.
The machine that is having network problems is a desktop PowerMac G5 (Dual 2 GHz model, running OS 10.5.8).
The problem that I am getting is that the desktop can detect the network, but it either can't connect to the network (it times out), or it connects but doesn't get a very functional net connection. On some occasions I have looked in the Network control panel and it is given an appropriate IP by the DHCP server, but the connection is either too slow to be usable or just non-functional. Other times it just never gets a valid IP. However, one thing to consider is that there have been (very) brief periods when I have been able to connect the G5 to the network and it has seemed normal, only to fail again within a short period of time.
I thought it was something wrong with the wireless hardware in the G5 machine, but if I connect to a MiFi instead of the AEBS, it works fine and I experience no problems with the network connection. So it does not appear to be a problem with the hardware.
Could this be some sort of incompatibility on the network? I thought that might be, except that an machine just as old (the Powerbook G4) running the same OS version has no problems.
Any thoughts? Thanks...

Answer 1

The problem that I am getting is that the desktop can detect the network, but it either can't connect to the network (it times out), or it connects but doesn't get a very functional net connection. On some occasions I have looked in the Network control panel and it is given an appropriate IP by the DHCP server, but the connection is either too slow to be usable or just non-functional. Other times it just never gets a valid IP.
Please try the following:
1. Delete Preferred Network(s)
o System Preferences > Network > AirPort > Advanced > AirPort tab
o Under "Preferred Networks," delete the network(s) you regularly use from the list.
2. Delete AirPort Keychain Entries
o Launch the "Keychain Access" application located in Applications/Utilties.
o Click on the "Kind" filter at the top, and look for any "AirPort network password" entries...and delete them.
o Restart, or log out then back in.
3. Add Preferred Network(s)
o System Preferences > Network > AirPort > Advanced > AirPort tab
o Add the preferred network(s) using the "+" button.
o Restart or log out then back in.
Please post back your results.