Potentially dumb question... my FreedomPop phone has started getting stuck on the "Sprint Spark" yellow screen. It doesn't always do it, but right now, it's 9 times out of 10. Prior to that, I was getting random reboots. It's not rooted, so this shouldn't be a custom kernel issue. The only suspect line I see in the boot log is "can't open /dev/tty0: No such file or directory". Does that mean anything?