I learned a hard lesson recently: Don’t use a KVM switch when trying to upgrade Ubuntu through the Update Manager. It caused the system to crash on me with two attempts to upgrade using that method. I decided to install Ubuntu 12.04 Precise Pangolin from scratch.
If you are accustomed to using a graphical user interface you don’t see all of the changes that take place when a USB device is connected to a computer. Each time a Keyboard Video Mouse switch is used to activate input to a system, it is like connecting the device for the first time that day.
This discovery might fly in the face of the premise these connections are supposed to bring to a modern operating system environment. Back in the days before USB, any changes to hooking up a peripheral device such as a keyboard, mouse, printer or scanner required shutting down the machine before making such a change. After two crashes in the midst of the process the system was unpacking and applying the new packages, having a system crash in the middle of an upgrade process can not be seen as a fluke. It should not surprise me really. USB demos have been crashing since the days of Windows 98.
Maybe it is just the model of my KVM switch or the fact mine is USB as opposed to the old PS/2 connections, but heed the warning: Using a KVM switch during upgrade to a new version of Ubuntu through the update manager can make you scream, “NOOOOOOO!”