Samsung Galaxy Player 5.0 won't turn on after messing with build.prop
Are you sure you're rooted?
If so, have you tried su -c chmod 0644 /system/build.prop? Or you can also try entering su first and then the chmod command next.

To pull the build.prop: adb pull /sdcard/build.prop
Or maybe you can just replace the one in /system with the one on your sdcard:

su
cp /sdcard/build.prop /system/build.prop
chmod 0644 /system/build.prop