Speed Racer may have put on the brakes at the box office last weekend (in actual fact, he barely even really got his gears running, grossing a worse-than-disappointing $18.6 mil in his debut). But it was full speed ahead for’s Summer Box Office Challenge. The big news from the fourth week of our big game was that only eight percent of all players correctly predicted that the speedster would wind up in third position — behind both the blockbuster Iron Man and the decidedly un-tentpole-ish What Happens in Vegas. What’s more, fully one in five participants failed to heed the warning of’s own box office analyst: They assumed Speed Racer would come in at No. 1. (Ouch!) Anyway, the week’s winner was one “ktcat1121,” who beat out “jamiele” and “nswank” in a tiebreaker.

Everybody should have better luck next weekend, when The Chronicles of Narnia: Prince Caspian premieres. Wanna play along (and have a shot at taking home some free DVDs)? Our Box Office Challenge is waiting for you to take a shot at ranking the weekend’s top 10 grossers by Friday at 8 p.m. ET. C’mon, get revved up!