Hi, i did several aptv2 but only experinced this 3 times ( all untethered , 4.3 , 4,4,4 and now 4.4.2) .
First one i had to restore, 2nd one i unplugged and plugged back for 5 times.
3rd time no Joy, rebooted several times, restored rejailbreaked still same issue. I have a 4.4.2, i red that some guys using snowbreeze had this issue, the screen goes black for minutes after the logo but then next reboot it works.
How to fix this?