nm-applet suddenly stopped connecting to some networks

[Joshua Spodek <joshuaspodek yahoo com>]

The context
 
 I am running nm-applet 0.6.5 on Ubuntu 7.10 on a Lenovo X61. It's worked great for a few months. Suddenly it partly stopped networking with my home wireless.
 
 When I first start nm-applet it shows the two-computer icon with an x on it in the panel. After about one second the x goes away, but I don't have a connection.
 
 The problem
 
 If I left-click the two-computer icon, the list of networks shows up with signal strength and the two-computer icon switches to the bars with all the bars empty and I don't connect.
 
 If I click my network, nothing happens except that the next time I left click the icon, the radiobutton for my network is selected. What used to happen was the nm-applet icon would switch to the trying-to-connect icon (two dots with moving arrows between them).
 
 Possibly related behavior
 
 If I go to the library across the street (where I am posting now), it connects, but it
 still never shows the trying-to-connect icon. The bars just fill up.
 
 If I connect on ethernet, it switches and works automatically.
 
 I don't know what caused the problem. It's possible using the library connection caused a problem. On this network Evolution can't send emails (but can receive them) and it occasionally blocks a site.
 
 Can anyone help? Should I provide more information?