I have a 1996 Omega, and it had the same problem, only on the drivers door for some reason. The problem was it had been stood unused for a while and the catch mechanism had seized. I just had to keep pulling really hard and after a few tries it opened. When you do get it open i'd recommend putting a lubricant (grease or equivalent) on the mechanism in the door and the metal latch thingy on the car and re-apply a few days later to make sure it doesn't happen again. Hope this helps.
Ben De Oliveira, March 2006
