wow my phone has been doing this for about 3 weeks! i think its a hardware issue too. ive done lots of hard resets and reflashed stock 6.5 rom twice. that doesnt do a thing... the first time i let it go to sleep, the screen will not turn back on and i have to soft reset. just like you, i am able to use the phone but the screen is not on... i now have my phone set so the screen never turns off
ive never had an issue like this and ive had a 6700, 6800, tp1, now tp2.