Piping bag disaster

The final birthday in March, and would seem the most straightforward - I've made cupcakes goodness knows how many times! However, I decided to go a little further today, and use a piping bag for the icing - again, I've done this before.
But today was a total disaster. the bag got clogged, so after applying a little more pressure, the buttercream icing went everywhere as the bag popped... I ended up dolloping icing on top of the cupcakes, not quite as wholeheartedly as when I started...