Pro Tools 5.1.1cs5 adds a new preference that allows the user to set the amount of time for timecode to line up before Pro Tools attempts to buffer the data. This preference is only for when Pro Tools is slaving to an external controller with remote mode. Under Preferences-Operation-Remote Mode, try setting "delay after play command" to 30 frames. Each controller will work best with a different setting so you'll need to experiment to find which setting gives you the fastest lock.