If you have a mac and use wireless to connect, you might expect that it will automatically join your wireless network after you tell it to “remember this network”. I know on my old powerbook it did, and on my girlfriend’s macbook it auto-joins too. So I started wondering why my macbook pro just wouldn’t do it. I searched the keychain and found my network in the login keychain, so I thought something really bizarre was going on. When I checked console (the console app in /Applications/Utilities) it said my network wasn’t in the system keychain!
To make a long story short (as my mother would say), I found a solution here: http://discussions.apple.com/thread.jspa?messageID=6757490
It turns out that when I moved System Preferences to /Applications/Utilities it broke my mac’s ability to add networks to the system keychain! I moved it back to /Applications, deleted the network from my network preferences and keychain and then joined the network again. This time the network was added to the system keychain and all is well!