To change build.prop you have to be rooted. And either download an app that does that and or browse to it via a root browser and modify it. Make a backup because if you mess up something your hosed. Soft bricked anyhow.
I don't have any problems however I would suggest clearing cache and data through settngs then apps. You are using your Sammy id right?
Current Phone: NeXus 5 D820