There was a version jump in mySQL, I don't know whether it was from 4 from 5 or a number within 4.x, that the default behaviour when dealing with too long input was changed. Before, strings that didn't fit into their varchar column they were silently cut off. After, an error was raised.
I'm having a hard time finding anything in the documentation or the change logs about this. Could somebody point me to the right direction where to find info on this?