if you have k750i white screen becouse of software dont' do full flash just following this step :
1. attach the ufs/n box
2. read gdfs
3. make sure all data oke
4. save
5. than write gdfs with data just save
6. skip format
7. ok.
8. disconnect cable.
your phone will back to normal with all data save.

cheers,

nulroute.