I am running Fedora 14 and just upgraded NetworkManager to 1.0.8.3.996 (AS per the yum history below:

Loaded plugins: langpacks, presto, refresh-packagekit
Adding en_US to language list
Transaction ID : 55
Begin time     : Wed Mar  2 13:50:07 2011
Begin rpmdb    : 2160:b8db87b8a6fdc2235600092c6c5a5f986fee7390
End time       :            13:51:06 2011 (59 seconds)
End rpmdb      : 2160:b7b353ba59e5d5395f94985a4eda22adb663791f
Return-Code    : Success
Command Line   : update
Transaction performed with:
    Installed     rpm-4.8.1-5.fc14.x86_64
    Installed     yum-3.2.28-5.fc14.noarch
    Installed     yum-metadata-parser-1.1.4-2.fc14.x86_64
    Installed     yum-presto-0.6.2-2.fc14.noarch
Packages Altered:
    Updated NetworkManager-1:0.8.1-10.git20100831.fc14.x86_64
    Update                 1:0.8.3.996-1.fc14.x86_64
    Updated NetworkManager-glib-1:0.8.1-10.git20100831.fc14.x86_64
    Update                      1:0.8.3.996-1.fc14.x86_64
    Updated NetworkManager-gnome-1:0.8.1-10.git20100831.fc14.x86_64
    Update                       1:0.8.3.996-1.fc14.x86_64
history info


After the update, when I tried to edit the wireless network settings, I
got an error message saying: 

"Error initializing editor
802-11-wireless-security"

And on clicking the OK button the editor box disappears. I eventually
logged in as root to try edit the settings, had the same issue. I then
deleted the wireless networks and tried to manually create a new one.
The creation worked fine, but now I cannot edit any of the settings.
Auto discovery of wireless networks and the rest of the system seems fine, after having deleted all wireless networks, but I still can't edit anything.

All the other tabs (wired, DSL etc.) seem to be okay.