Last night my HTC Thunderbolt displayed a blank black screen and I couldn't get it back to the desktop. I had to remove the battery to shut it down. I turned it back on and it took longer than normal for it to boot up. Now i when i turn on my hotspot it show that it is on but I do not see the normal icon and when connecting my device it show connect but no internet. Now I also can not power off my phone when holding the power button. I do not get the regular menu that provide me with the choice to power off.