When using Instant Messanger and what you say to someone is missunderstood and everyone gets confused. So you say DIM and that means it's all messed up, let's forget it and restart the thread - it is the IM's fault things went off course. Like striking record in court.
during IM she gets angry at something he said and has been discussing. So he says DIM and she forgets it all and lets it go, cause she knows it's some form of misscommunication and the IM is to blame