How can I fix my wireless connectivity

I have a 2.1ghz Macbook, model number 1181.

The wireless connection is extremely flaky with this computer. The wireless connection with fine with other devices, including 2 iPod Touches, a mac mini, an old G4, and various PC laptops.

The Macbook's problem is that wireless connection is not steady. Upon turning it on or waking it up, the connection is fine for about a minute, the Airport display shows full strength in the menu. Then everything just drops out. The Airport drops in strength, showing only one or two bars. Connecting to anything via the internet becomes impossible, the web browser displays messages that say it's not connect to the internet. If I click repeatedly on the Airport display in a rapid fashion, that seems to improve connectivity as long as I keep clicking.

After an indeterminate amount of time, somewhere between 15 minutes and half and hour, the connection steadies is generally more consistent. If the computer is turned off, put to sleep or switched to another user, the problem begins all over again.

'''Notes on things I've tried to fix this:

'''The Macbook is running the latest addition of 10.5.

This happens in Firefox, Safari, Opera and Camini.

I've tried deleting all known networks and starting from scratch with just the home network.

I've tried using different channels on the Wireless router

Interference robustness is on.

I've tried placing the Macbook closing to the router, but that doesn't help.

If the Macbook is plugged into the LAN via Ethernet, the connection is strong and steady.

This occurs with three different routers: An Airport Extreme, Airport Express and Linksys router.

Anyone have any suggestions how this can be fixed?