Could be something to do with the update to the new kernel (.18 ) since others are having trouble too. When I try to connect to a wireless network, the popup tip just says "Waiting for network key". In the good old days the dialog box for the keyring password popped up. Now: nothing.

Initially, I thought my wireless was down. I reinstalled network-manager, network-manager-gnome, and wpasupplicant. Didn't help. In /etc/network/interfaces, commenting out all lines except the "lo" related ones (as per this post) at least got the wireless networks to show up again in nm-applet, but it still didn't access the keyring.
$sudo /etc/init.d/networking restart
finally got me the dialog to enter the whole WPA1 passphrase and then make a new keyring. That's about ten minutes of messing about every time I want to use wireless!

It's probably this bug, wpasupplicant doesn't start when network starts? But, if so, that is a HUGE ISSUE! There needs to be a red sticky telling us that the devs are working on it, and especially what, if any, is the best, simple workaround.

Wieman01 has an excellent post about configuring without using network-manager, But I've had rather poor luck doing anything with my wireless manually, and after all the fighting with the network the last couple of days, I want to be sure anything I try will work!