Are you using a 5V or 3.3V FTDI Cable?
Are you able to see the Serial Port in the Device Manager (Windows) or in /dev (Ubuntu)?
Did you update the firmware of the board?
Are you using a 2.0 or 3.0 USB port?
Which settings are you using on Putty?
In Ubuntu are you using sudo screen /dev/ttyUSB0 115200?
Are you having the same behavior when you boot with and without the SD card?