My Thunderbolt won't turn on. (Got this phone June 2011.) When I press and hold the power button, the white "HTC" screen comes up. After 11 seconds it vibrates once. 5 seconds later the screen goes dark. 5 seconds after that the white "HTC" screen reappears and the same loop occurs. It never gets to the "Thunderbolt" screen. The only way to make the loop stop is to remove the battery. After replacing the battery, I try to turn it on and the same thing happens.
I have two batteries. Neither solves the problem, so I don't think it's a battery issue. Going through all this with the charger plugged in makes no difference. Have tried leaving the battery out a couple of hours -- no difference.
Anyone have any ideas?