Rarely are they this serious, but sometimes translation difficulties can have serious consquences.
I remember this incident from news reports at the time, but they didn't go into the detail of this Wiki article about it--or at least, I don't remember it, if they did.
"The crew was reported to have asked for 'priority' landing which, due to language differences in English and Spanish, can be interpreted as an emergency to the Spanish speaking pilots but not to the English speaking Air Traffic Controllers. This may have caused some confusion amongst the pilots when the ATC confirmed their priority status."
Read the whole unhappy story here, some of you may remember it: http://en.wikipedia.org/wiki/Avianca_Flight_52