Dell precision M4700: Wireless failed after ubuntu 12.04 updating

[rbaena]

Hello everybody,

hope somebody can help.
I am working on a Dell precision M4700 laptop with Ubuntu 12.04 and KDE desktop.
After a "suggested" system updating, my wireless connection stops working. KNetWorkManager sees the wireless and tries to connect to it but, after a while, a small windows pops up and asks for a password. If I introduce the wireless one I have it tries again but nothing happens. That window appears again and again asking for a password.
Such windows has a key as a symbol on the top left corner, the same key appears over the KNetWorkManager symbol which is on the bottom panel. The window has the title "Secretas de [wireless name] - Service for KDE-" (in Spanish sorry ).

I guess some security measurement has been activated after the updating but I do not know how to deactivate it.

I am sure the password is correct and the router is working fine, indeed, I am using another laptop to publish this thread using the same wireless connection.

I also post some useful information:

kernel: 3.2.0-37-generic
desktop KDE
ubuntu 12.04.2 LTS

iwconfig:

lo: no wireless extension
eth1: IEEE 802.11abg ESSID off/any
Mode: managed access point: not-associated
Retry long limit:7 RTS thr off Fragment thr off
power management: off
eth0: no wireless extension

Thanks for your support!