An innocent update this weekend to my Fedora 15 (KDE) system broke the Wireless Connection. The culprits – NetworkManager 0.8.9997-4.git20110620.fc15 and NetworkManager-glib 0.8.9997-4.git20110620.fc15. To make matters worse, anything I did within Network Manager crashed Plasma.
To fix this problem, I first setup a wired connection and then reverted both packages to their previous versions 0.8.999-2.git20110509.fc15, using this command
yum downgrade NetworkManager*
There is a forum link here which discusses this problem.
The official bug report: https://bugzilla.redhat.com/show_bug.cgi?id=716591