List of Wireless Networks disappear/don't show

Question

I'm having major problems with my Macbook Pro. It has all the latest upgrades for Leopard (just checked again for updates - nothing more available). This was a native installation of Leopard - not an upgrade from Tiger.
When I FIRST start my laptop, it connects to the #1 preferred network. But I have 2 routers at home (and I live in an apartment so there's about 12 networks around me) and I often need to switch depending on which end of my condo I am in (concrete walls suck for signals). Any how this is not a signal issue however, as this problem happens when I am in the same room as my router.
When I click the Airport button on the top, the dropdown menu comes out, and fora split second it displays all the networks. But after about half a second (which is NOT enough for me to find and click another network I need to hook into) the list disappears, and truncates to the one I am already on.
So from there I tried "Join Other Network" and it opens a new window, asking me to enter a Network name and what not. When I click on "Show Networks", it used to display all the available networks, but it displays NOTHING - not even the network I am already connected to, using fast and normal internet.
So basically I need to turn my Airport off, open the preferences, change the order of preferred networks on the list of saved networks, and then turn it on again.
Now here's the killer - 50% of the time, after reconnecting, or after waking up from sleep mode, my laptop will FAIL to find internet connection from any of my two routers (while my roomates are doing fine) even with the proper IP addresses and Subnet masks assigned. it basically looks like a healthy connection but I get no internet browsing, email, MSN, nothing.
So basically every time I move from my living room to my bedroom, there's a 50% chance I need to reboot my computer. And there's a 100% chance I need to stumble around settings to make sure my computer finds the right router.

Answer 1

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.