I have encountered a bizarre problem with my hero. I have two At&t sim cards both work fine in other phones, but one of the sim cards would cause the Hero to boot up with airplane mode turned on and it cannot be turned off, so I can't get a signal. However the other sim card also from at&t works fine(identical cards and cellphone plans). I am 100% sure that the sim cards are in good condition and have tested them in other phones. I have searched everywhere but couldn't find an answer. Any help would be deeply appreciated. Thanks!