Happened to my VW Caddy van on Thursday evening ......

The drivers door was actually frozen to the body.
To make matters worse, I got in through the passenger door, and in the ensuing mayhem, snow fell off the roof on to the passenger seat ..... !

Drivers door released yesterday morning by spraying around it's edges with a whole can of de-icer. Try a light coat of petroleum jelly on the surround rubbers - should do the trick!