Welcome to NICO Marty.
Does the seat click at all when you try and move it forward, or does it try and move one side but not the other? There could be a piece of foreign material stuck in the track, or there is a gear that commonly fails on these cars (on the FX and G).
There is a place that sells replacement gears if that's what the issue is (could be, it's common).
http://www.odometergears.com/products/I ... Present/98
Here is a replacement guide. Looks a little involved, but better than going to the dealer.
http://www.odometergears.com/documentat ... cement.pdf