It is a parameter problem but I can`t remember which.It`s not the one that looks obvious.
I`ve had this on a Chiron which also uses an axis drive on the 610 to drive the spindle.
You could also adjust the tacho pot on the drive but it`s not the correct way.
What machine,motor and drive?
EDIT: Silly question,you don`t have the spindle overide switch turned down,do you?