Less than a month after the release of the Sprint HTC EVO 4G, many of the smartphone’s users recently found their devices rendered completely inoperable. That’s because a firmware update released by Sprint this week seems to have gone badly awry for an unknown number of the customers who installed it. For those customers, the firmware update has “bricked” their phones — a term not so affectionately used for phones that behave more like doorstops than multifunction communications devices. The screen is blank, the signal is gone, the phone is dead.