WD TV SMP keeps losing username password to WD MBL

Try pressing the reset button on the bottom side to restore the WDTV configuration back to default. If the problem continues try rolling back to a previous firmware version and then reinstall the latest version again. Check the link below for more information. 

How to roll back the firmware on a WD TV Live Hub Media Center or WD TV Live Streaming Media Player 

Also see if the following thread helps. 

http://community.wd.com/t5/WD-TV-Live-Streaming/How-to-resolve-quot-Network-shares-quot-access-problems-with/m-p/671513#M27826