Guess what? It happened to me this week. Because of a rather simple thing, actually. In my development machine I have mySQL 5, and the server machine has mySQL 4. My beautiful queries were all failing.
It actually took me about 2 minutes to fix the problem. Get the latest running version from source control (I'm currently using SVN) publish it and that's it. And during those 2 minutes I just kept thinking, "I'm *so* glad I have this in source control!"
Listen to experience. Use source control. Always!