This wasn't in the context of moving to another culture, but it was amusing all the same.
I was learning Spanish, and as a part of my interactions in the class, I was going to say "Will you go to bed soon?" The verb for this is acostar, which literally means to put to bed. So when you say "I'm/He's/She's going to bed", you put a reflexive pronouns in front of the verb, in essence changing the verb to "I am putting myself to bed"
The correct way to say what I was trying to accomplish would have been "Te acostarás?", meaning "Will you put yourself to bed", or "Are you going to bed." What I did was use the first person form of the verb ("Te acostaré"), which changed it to "Will I put you to bed?"
My teacher at least has a good sense of humor about it; probably wasn't the first time he'd had it happen.
edit: funny, by the way, how all of the mistakes so far have had some sort of a sexual connotation...as a modern psychology student, I hate to quote Freud, but...