I definitely 100% agree it is a residual code from 3.4 because my wife never downloaded 3.4 .....and can get on there .....I can go in as a guest just not login 3.4.1 on my phone.....I tried all u mentioned above including move to sd card but no luck....something not allowing 3.4.1 to install correctly...I'm do for a new phone upgrade I think ....only thing I think that can solve the problem