Which has sort-of happened already in history of space exploration, when Mars Climate Orbiter mis-handled Mars orbitial insertion and was lost. The problem was traced down to mis-match of measurement units used in software (Newtons vs. Pound-force).
http://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Cause_of_f...
Ugh, we get it, everyone thinks they're being cute and its a way to mock US units. Yes, yes, this isn't getting incredibly tiresome.
"The error had occurred when a symbol was being transcribed by hand in the specification for the guidance program. The writer missed the superscript bar (or overline) in [the formula] by which was meant "the nth smoothed value of the time derivative of a radius R". Without the smoothing function indicated by the bar, the program treated normal minor variations of velocity as if they were serious, causing spurious corrections that sent the rocket off course. It was then destroyed by the Range Safety Officer."