Trinity, the latest content update for the sci-fi MMO EVE Online, is overwriting an important boot file required by Windows XP. As you can guess, the bug prevents affected systems from starting. Not only is this stopping people from playing the game, it's making it rather hard for them to do much with their PCs at all.
There are three ways to update to Trinity - using a classic patch, classic to premium and full premium. It's the second of these that's causing the problem. The update comes with a file called "boot.ini", which just so happens to be the exact same name for a critical file of Windows XP's bootstrap. For some reason, the update overwrites this file, even though it resides in a completely different directory.
Only Windows XP machines are affected, so Vista users and users of older versions of Microsoft's operating system can sleep easy.