In response to dozens of complaints about a mean glitch found within Gears of War 3, Epic has released a statement on their official forums in an attempt to calm the fans' rage.
The issue stems from Horde mode when players attempt to start a game with 2 profiles signed in. The glitch will cause the game to crash in menu screens and will even corrupt profiles keeping players from entering any game mode with that profile. One of the forums reps who goes by the name of Rykard stated that the studio was indeed aware of this issue and that they are doing everything they can to resolve it.
Hopefully Epic Games will be able to solve this issue soon as Gears of War 3 is so loved by many fans.
Source: Epic Games Forums