I have the same problem with one of the drum brakes on my car.
I use my car for work daily, which involves stoping at houses all day, so hand brake is used alot.
I find if I leave the car for more than 4 or 5 hours with the hand brake on . The back right drum brake locks solid and wont release.
The only way to release it is to try and pull away forward, then reverse then forward etc etc until you hear a bang and the wheel releases!!

But it doesn't work on gravel driveways, it just drags the rear wheel along, and leaves a big trench!
I am off on holidays in a week or so and plan to get it looked at then.