I just encountered severe problems with the wireless card on my Lenovo IdeaPad S10-3t. While my netbook connected to the access point I could not use the connection in the common sense, so not even a ping within my network arrived.
While playing around a bit, trying to understand which kernel modules are installed and how they were built, I encountered that the recent update to Kubuntu Trusty Tahr also installed new drivers. Maybe this problem doesn’t exist for a fresh install but only with the update. Who knows…
I found the solution on http://askubuntu.com/questions/55868/installing-broadcom-wireless-drivers.
The surprinsingly simple solution for my specific hardware (I have a Broadcom BCM414 with the PCI id 14e4:4727) is to remove the bcmwl-kernel-source package and just use the drivers shipped with the linux-firmware package.
Now Wifi works again, but my netbook is complaining about having found proprietary drivers which might be required to grant access to all my hardware’s functions. I will find a solution to get rid of this message.