Discover a work around for bug in OS X 10.9 where under some circumstances when full disk encryption,Filevault and mobile account features are enabled the system prevents the user from selecting a specific user using the mousepad, thereby preventing the user from authenticating and unlocking the disk, prior to being presented with the standard login screen for the user account.
Indicators that you are experiencing this issue:
Upon startup there may be two user accounts for your single mobile account enabled user. Caps lock key works, indicating that the keyboard is functional, however the mousepad will not register clicks, it will only move the mouse.