Did you do what the thread suggested.
1) Remove the console from running on the serial port (Edit the cmdline_v6.txt or cmdline_v7.txt depending on your board)
2) Remove the startserialtty from /opt/bootlocal.sh
If you are using a rpi 3, you might want this note
UPDATE: The raspberry pi 3 has changed things around a bit: ttyAMA0 now refers to the serial port that is connected to the bluetooth. The old serial port is now called ttyS0. So if you have an RPI3, everywhere you see "ttyAMA0" below, you should read "ttyS0".