Mariner 1 launched on Juy 22, 1962. It was intended to do an unmanned fly-by of Venus to collect scientific data, but an error in the computer codes caused it to veer off-course. This was NASA's first planetary mission, and it was losing to Russia in the already contentious space race.
As it turns out, a misplaced hyphen seems to have caused the rocket's trajectory to be off. A NASA range-safety officer wanted to avoid any possible crashes back down to Earth, so 293 seconds into the launch, he blew it up. The coding blunder cost NASA $80 million (in today's money, that's $673.4 million). There were conflicting reports, some of which blame a misplaced decimal, and others stating that a hyphen caused the error in trajectory.
Luckily, Mariner 2, a backup rocket, was already built and waiting just in case disaster struck. That one completed the mission successfully, but Mariner 1 would always be remembered for its critical error. Science fiction writer Arthur C. Clarke called it "the most expensive hyphen in history."