I am going through the exact same thing. I recently went through
anUbuntu upate and a later version of the kernel was loaded and this
went into my grub startup list as the default. I began to
see "Network Disconnected" for the first time. I restarted to
booted with the earlier kernel that was still in the startup list
and the network connected fine. I am using a new Toshiba Satelite
laptop. P.S., I am still having no luck with my Atheros wireless
card that is built in.