vauxhall auto box?

I got a vectra-b 98/99 with autobox. the problem is that car will sit and rev nice in P, N but when you engage the rest of the gears R, D, 1, 2 it will stall straight away. itused to only stall when you come off the brake
if you give it a good rev as you come of the brake you can get the car going but it doesn't change gears properly.it takes long to change up butthe kick dwn is gd.