Charlie on the MBTA writes that after just four days of use, his CharlieCard died:

... Neither the faregates at Harvard Square or the vending machines could read the chip. The (customer service agents) tried to solve the problem but alas I was told to go to the new CharlieCard Service Center located in the concourse at Downtown Crossing (located on the Red, Orange and Silver Lines) When I got there I wasn't alone and it took about 25 minutes to see a clerk. ...