Here's a surefire sign that Hollywood's summer blockbuster season has come to an end: A four-week old film has reclaimed the top spot at the box office. The Mel Gibson alien thriller Signs which was released on August 2 climbed back to No. 1 with $14.4 million ($173.2 million to date). After a two-week reign, Vin Diesel's XXX slipped to second with $13.7 million ($106.7 million to date), followed by Spy Kids 2 (No. 3 with $7.8 million), sleeper smash My Big Fat Greek Wedding (No. 4 with $7.6 million) and Blue Crush (No. 5 with $6.5 million). Meanwhile, all three of the weekend's major new releases the Elizabeth Hurley-Matthew Perry comedy Serving Sara (No. 6 with $6.1 million), the Wesley Snipes-Ving Rhames boxing drama Undisputed (No. 8 with $4.7 million), and Al Pacino's virtual reality flick Simone (No. 9 with $4.1 million) opened poorly.