Wireless Connectivity Intermittent

MacBook Pro 2.33 GHz Intel Core 2 Duo
OS 10.5.3
AirPort Extreme Card w/ Firmware 1.3.5

I've been having the following problem for a while now.

My wireless connection has been spontaniously becoming unreliable. What I mean is, I'll be logged onto a wi-fi network and everything will be working just fine. After a while, the connection will drop out. The Airport icon will grey out, like when it's not connected then it will re-connect, then drop, etc. Sometimes, when I click on the icon, I see that it isn't seeing the network, then it will, then it won't etc. It doesn't seem to be related to the source network as the problem has persisted across several networks and other computers on these networks doen't have any problems.

When my laptop is sharing an internet connection via the airport card to my iTouch (or another computer), I have the same problem. Everything will work fine for a while then, my iTouch will stop seeing the laptops broadcast. It will drop in and out.

Its like the card is turning itself on and off, back and forth if that makes sense.

Sometimes, power cycling the computer will fix the problem. Sometimes not.

Does anyone have any ideas what might be going on?

I've been wondering if its as simple as reseating the card but I have yet to figure out how to access it on this machine.

This sounds to me like a possible hardware problem. Any AppleStores or similar nearby with Genius desks who could help you locate the card?

Is it possible to reapply the latest Firmware update?

You could try to trash the Airport prefs in /Library and ~/Library but I doubt it'd help.