Please use the “NitoTV” app which ships with ATV Flash v2.3 and install the package “5.3/6.1.4 Untetherd”. After that you can either reboot your ATV via pressing the menu and play buttons on your Apple Remote or you can power recycle your ATV2. You will no longer ned to coonect your ATV2 vis USB to a computer for reboot. I have trired this on my ATV2 and it has been working flawlessly for 48 hours now. No need for any previously saved firmware signatures.