Lion 10.7.3 update may solve WiFi network confusions?
Euan Williams
This post may have a bearing on Mike Corgan's recent WiFi network woes, but is posted as a separate topic for everyone.http://osxdaily.com/2012/02/15/fix-for-mac-os-x-not-remembering-wireless-networks/
Quote
<Mac OS X Lion stopped remembering a specific wireless network, forcing me to manually select the connection and then enter the password each time I wish to connect to that wireless router. This appears to be a common enough issue with wireless connectivity in OS X Lion and it usually occurs when waking from sleep or rebooting a Mac, which is followed up the connection failure>
Unquote.
The fix depends on updating to 10.7.3, using Disc Utility to repair permissions and then rebooting. The article offers links to a large selection of other WiFi tips. Let us know if this fix works for you.
If you are having troubles with 10.7.3 (or any other system update) it may be necessary to reapply it but by using the Combo updater from Apple's support / downloads site. This is big, at around 1GB but Combo updaters install new files rather than patches to existing ones, and takes Lion 10.7.0 right up to 10.7.3 in one go.