Airport Extreme Network (Wired) Dropoffs

Question

Hi everyone,
I've been suffering with a problem with my Airport Express for as long as I've owned it and finally decided I would make a major step to resolving the problem (primarily held back by not wanting to purchase another router to prove the problem).
I run a home Wireless network consisting of 2 x G4 PB 1.33 12" with Airport Extreme built in and 1 x Mac Mini with Airport Extreme built in. All devices connect to the Internet via this Airport Extreme which I have configured in NATing mode running DHCP. The Airport Extreme connects to the Internet (3Mbit/s Cable) via my Motorola Surfboard SB4100 Cablemodem using the Ethernet port. In between the cablemodem and the Airport Express is a 5 port 10/100 Switch, that enables me to connect my PS2/Xbox/GCN to the Internet (I have 2 Internet IPs, one for Gaming and one for Airport).
I have the Airport configured so that when there is activity the light flashes.
The problem I was getting was that occassionally (sometimes every 30 mins, sometimes more, sometimes less frequently but always frequently enough that I would be interrupted while doing things online) the connectivity to the Internet would pause. The pause was typically 10 seconds, sometimes less but never more than 20 seconds. While the Internet paused the light on the Airport would go orange and flash, as though it'd lost its IP address or something. Performing a hard reset on the device would not affect the reliability of the Airport and this connection and also up and downgrading the firmware from 6.1.0 to 6.1.1 to 6.2 does not affect the reliability either.
When I check the log of my surfboard occassionally I see sync'ing errors and put the problem down to this, however there were certainly less errors reported in the SB4100 log than there were downages.
I put the problem down to an IP renewal problem (where the Airport was renewing the DHCP lease) and kinda tried to tolerate the outages even though they are really annoying.
I had the opportunity to get my hands on a Cisco PIX 501 cheap the other day and took advantage in an effort to perhaps irradicate this problem or just perform some testing and my results are even more bizarre.
Now I have configured the PIX 501 to perform all the NAT/PAT functions that the Airport used to perform along with DHCP, etc.. The Airport has been configured purely as an Access Point, only bridging between wired and wireless.
The problem is still occurring in the new configuration!!
What I have found, though, from the indicator lights on Cisco PIX (indicating link speed and activity on the 4 ports of the integrated 10/100 switch) is that when the Airport goes "funny" the link light for the port that the Airport connects to goes out until the Airport goes back to green on its LED.
To me this looks like there could be an intermitted fault with the Ethernet interface on my Airport Express or a dodgey Ethernet cable. So I replace the Ethernet cable with a brand new 2m CAT5e cable to test this, and as expected the problem is still present. Next just to confirm absolutely 100% I move the Airport to a different port on the PIX and plug my PB directly into the old port (Disabling Airport) and test connectivity. I do not get a dropped link on that port and when the Airport is dropped I can still connect through the Cisco using my wired connection.
When I spoke to Apple they said that I should switch firmware versions to 6.1.1, then 6.1.0 and then back to 6.2 which has not helped either.
As a little quirky puzzler I can also force the problem to manifest itself by using Remote Desktop Protocol to connect to either a Windows Terminal Server or XP machine through the Airport. When I do this the problem will appear within minutes and recur every couple of minutes but not with any real regularity. Unfortunately for me this is something that I do very frequently
Before I try and take this unit back to Apple has anyone else seen this kind of problem and possibl

Answer 1

My apologies, perhaps it's not clear. The Cisco PIX is a router/firewall device. This is exactly what I have done and the problem is clearly nothing to do with anything except the Airport as my investigations and testing have proved.