Hi,
If the method outlined by Campy doesn't work instead of the water soaked sponge try steam.
Boy am I in trouble if my wife reads this!! My wife has an iron the connects to a large remote water supply and can blast continuous steam for ten feet. I think it is also useful on clothes.
I had a similar problem and when she was out of the house
used the steam to lift a decal that was one bay out (got to change these glasses). The decal lifted after about five seconds of the steam assult. Like Campy described it wouldn't stick properly again and I used thin CA on the edges to make sure it stayed in place.
Good luck,
Colin