Most of the desktop computers in the UK's Department for Work and Pensions were paralyzed for four days on Monday, when a failed upgrade took them offline. The outage, covering 75 percent to 80 percent of the DWP's 80,000 PCs, is one of the largest in the UK government's not entirely impressive IT history.
And possibly one of the most costly. According to staff reports, the outage occurred on Monday afternoon, disconnecting staff e-mail, benefits processing, and Internet and intranet connectivity. According to one, a limited network upgrade from Windows 2000 to Windows XP was taking place, but instead of this taking place on only a small number of the target machines, all the clients connected to the network received a partial, but fatal, "upgrade."
News source: eWeek