Motor Suddenly Stuck

[braol]

This is really weird: I've been driving my '31 Model A all summer. Last time was 4 days ago. I get in the car tonight and it started to turn over for a split second and then stopped. I thought the battery was dead but light are good. I then, with the brake off, I then tried to rock the car in gear with the plugs out and the engine won't spin. I can't hand crank the engine either...like it's seized. I never heard of a perfectly fine running car suddenly suffer a seized engine. the last time I drove it I literally drove around the block and then home, not like I was on some long road trip and melted the engine down without oil in it or something. Any ideas?????