On Thursday evening I starteded the upgrade of my wife's computer from Kubuntu 12.10 to 13.04. Unfortunately when I finished the upgrade the next morning, it seemed that one of the DBus packages was broken, and not only could I not log into KDE, but there was no networking either.
I tried to do one or two quick things before heading off to work, but ran out of time and had to leave it. My wife was very gracious and "endured" using her phone the whole day for Facebook, etc (she has a Samsung Galaxy S3 mini).
That evening when I got home, I proceeded to try to get the networking up and running from the command line, so that I could fix whatever packages seemed to be broken and restore my wife's computer to a working condition. I struggled for about an hour and a half trying to figure out various command line options for wpa_supplicant and what the error messages meant.
After asking around in the #ubuntu-za IRC channel, someone asked why I needed to get my wife's wireless network card running. I explained that even though she was using a desktop machine, most of the networking equipment was out of reach, and I didn't have any cables long enough to reach her computer. Then someone asked if I'd tried to use my Android phone with USB tethering.
In about 3 seconds I had my wife's computer connected to my network and reinstalling the broken package. How silly of me not to think about simply using my phone to get her computer on the network. It really was that simple.
By the way, the package that was causing all the grief was qdbus. For some reason the binary was corrupted, and a simple reinstall of the package fixed everything; networking, logging in, everything.