iPhone 4S wth update 8.1.3 I updated my iPhone with the iOS update 8.1.3, and now I am unable to activate my phone because it shows a connect to iTunes screen with no other option.  

Finally, when I connect to iTunes, it gives me a message to update or, if it is still not working, completely restore to factory settings.  

Although there was no warning that this update is not suitable to my iPhone, now I have no other option than restoring my iPhone to factory settings. Worse, the update fails with error -39

Question: How do I fix my iPhone since it will not start up at all and this error -39 doesn't help me know what's really wrong and if it's my iPhone or my Computer that needs fixing?
Try to put your device in DFU mode, then restore it via iTunes. This method should work with you.