Happens from time to time, I normally keep jiggling the levers while moving the seat until it starts working again ok. Has worked in our car so far.
If you just cannot get it to lock into position fore and aft you may find that a little piece has broken and come out down at the runners. Quite common. A new seat is then the real answer although it can be fixed in one postion by drilling, then using a nut and bolt.
ChicksFan, January 2010
