Airport doesn't connect to preferred network

[automandc]

Bumping this solution since it is still valid for this problem when occurring under the latest system update (10.5.7). Not only was my computer not reconnecting to the preferred network, it was also waking from sleep several times whenever I closed the lid. I knew this was related to the airport, but could not solve the problem. I deleted preferences/preferred networks and passwords several times, but that did not fix the problem. Following the linked directions, which included the step of moving the System Preferences application (back?) to the /Applications folder (from /Applications/Utilities) fully resolved all my airport related issues.

[morre]

Thank you for the tip. When moving system preferences to the application folder it all worked like a charm again. I am though stunned about why apple does not inform about such basic thing to make the computer work....

Anyhow, thanks!

Markus