The sale of Electrolux vacuum cleaners was a wee bit disappointing after they advertising campaign under the slogan:
Nothing sucks like Electrolux!

The next one works only for those who speak Finnish:
There's a user interface generation tool called SCADA. A Finn would say this is pronounced: "Skeida" which means nothing else but shite.
I met the software 30 minutes ago at a lecture. The lecturer asked if we are familiar with SCADA. Few funny faces there, eh..

New additions:

In French speaking countries Toyota's MR2 model wasn't that great success because MR2 is pronounced "merde" i.e. shit.

Nokia advertised their mobiles in Germany using slogan "Jedem das Seine" ("to each his due" or "to each his own") but te text appeared also above the gates of the concentration camp of Buchenwald!

Pepsi made a double-slip with it's slogan "Come alive with Pepsi generation": In Germany it was translated: "Get up from the grave with the help of Pepsi" and in Taiwan: "Pepsi reanimates your ancestors".

Coca-Cola wasn't any better in China where they tried to get the use of Chinese signs. As the result they advertised "a wax filled horse".

Spanish world has been difficult market area both Mitsubishi and General Motors. The former's Pajero model translated "wanker" in Spanish and the latter wondered why Nova model wasn't selling as expected. Well, the translations for "no va" is "not moving". Also Ford's Caliente was a mistake. Althought it means "hot" in official language street-talk has another meaning for it: "Whore"