Back in 1977, President Jimmy Carter was in Poland for a state visit. Seeking a translator for his time there, the State department hired Steven Seymour, who was a freelance linguist who was known for his expertise with translating written Polish. That expertise in dealing with Polish on paper, didn't translate into expertise inspeaking Polish. During Carter's opening speech, Seymour translated the the English, "I have come to learn your opinions and understand your desires for the future." into the Polish, "I desire the Poles carnally."
While that one mistake would have been bad enough, Seymour's didn't end there. Carter started talking about how happy he was to be in Poland, which was translated as he was happy to grasp Poland's private parts. Further on in Carter's speech, he talked about his departure from the U.S. which was translated, "when I left the United States never to return...". Lastly, Carter went on to praise the Polish constitution of 1791 as one of three great documents in the struggle for human rights. What Seymour told the Poles in attendance was that their constitution was to be ridiculed.
Reasonably enough, the Polish people were left in that strange mix of anger and confusion that comes from when the leader of one of the most powerful countries in the world tells you that he wants to fondle you and your constitution is awful. However, the Poles weren't just angry because of just the translation. When Seymour did his awful translation job, he added a insult to injury by using Russian syntax and Polish idioms that had been out of style for 100 years. Also, keep in mind, this was the middle of the Cold War. Using any thing Russian is not the best move to make when you are translating to a people who were firmly behind the iron curtain and were being oppressed by the Russians. Not to mention that the Poles have a long history of not liking the Russians generally.
Now Seymour was rightly fired after this debacle, but the Carter administration wasn't out of the woods yet. Looking for another translator, they hired Jerzy Krycki, a former employee of the U.S. Embassy in Warsaw. Krycki was assigned to translate for Carter at a state dinner. However, there was a slight problem. While Krycki was fluent in Polish, his English wasn't the greatest. So when Carter got up to give the toast, he was greeted with only silence from Krycki. Carter, thinking simply that Krycki had missed his que, spoke the second line of the toast and waited. Greeted by even more silence, Carter knew something was wrong. It turned out Krycki heard the president just fine, he just couldn't understand the president well enough to translate for him. Since he didn't want to repeat Seymour's mistake of mistranslation, Krycki just chose to remain silent. Fortunately, the Polish leader's translator stepped up and translated for the president.
Fortunately for Carter, no other major mess ups happened during his trip abroad. As for both of the translators, they seemed to recover professionally after the incident, with Seymour continuing his work as a translator for poetry and Krycki working for a news agency. I guess the most important lesson to take away from this is you need to know what others are saying when they speak for you. Otherwise, you might end up propositioning and then insulting an entire nation.