A new patch for the online game "EVE Online" makes it impossible to boot Windows XP. Apparently, an extra backslash in the installer causes it to delete an essential system configuration file.
That QC team must be feeling embarrassed. I know I always hate it when I miss a subtle little bug like hosing the operating system.
I suspect that what happened here is that they tested the patch itself, but neglected to test the installer. And that probably happens more often than it should - perceptually, the installer isn't part of the "real" software you’re testing, so it's easy to overlook. The moral of the story: Don't forget to test installation scenarios.