Are you sure it was early 2000s? It might be Quantum Apocalypse, which has a very similar plot - the autistic man has the solution but of course is not initially believed but saves the day at the end.
uring routine administration at the Lyndon B. Johnson Space Center, Dr. Rhodes discovers that a comet has suddenly veered off its orbit and smashed into Mars. The explosion causes debris to travel towards Earth with the possibility of causing an extinction level event. At Ben Marshall's house, Ben refuses to give his son, Leo, a ride as he complained his own car smelled of mildew. However, Ben drives Leo to school and discovers Leo is in love with a fellow student, Lindsey. Leo is chatting with Lindsey when her ex-boyfriend, Sean, gives them threatening looks.
Terry, Ben's autistic brother, refuses to let Samantha, Ben's daughter, take the school bus, which is having mechanical problems. Lynne, Ben's wife, comes home to discover that and drives Samantha to school. They are caught in a traffic jam caused by an incident involving the school bus.
Along the way to Houston, Ben and Terry encounter a broken down vehicle. While trying to help, Ben is attacked, but Terry takes out the attacker, and they continue on their way. Ben suffers a heart attack, but they manage to reach the Space Center. They gain entry because Terry knows Dr. Rhodes's verbal password. Terry manages to convince Dr. Rhodes of his calculations, which was shown to be accurate. Ben dies from his heart attack.