When you created the magnet did you have the hair prop selected? If at some point the magnet became un-parented to the hair object, or if was never parented to the hair object, that might be the cause of the problem.

When you use Y-Trans did you have the magnet itself (as opposed to the Mag-zone or Mag-base) selected?

Sounds like you know what you are doing, so most likely you overlooked one of the basics...that's what I do anyway.