He was riding the scooter to the set when a car cut him off and they collided. TMZ says he was doing about 60 . . . and after impact, he was thrown from his bike, and his helmet struck the car's windshield, causing it to SHATTER.
It's unclear whether George was still WEARING the helmet when it broke, or if it'd fallen off. Sources say George was hurled 20 feet in the air, and actually flew OVER the car that he hit. TMZ says George's rep has confirmed these details.
In any event, he was rushed to the hospital, where he was treated and released within several hours. He underwent a CAT scan as a precaution . . . but apparently he was fortunate enough to walk away with just scrapes and bruises.