Sometimes, when things are particularly bad, you want to place the robber on a spot that you have a settlement/city on (i.e. if someone close to winning has one of your tiles as their most highly producing tile). In that case, the game gets confused because you placed the robber on yourself.
For example, if there is only one other player on that tile, the game still gives you a window offering a choice of who to steal from even though there is only one possible choice. On top of that, the options show that other player twice, and it takes some extra clicks in order to get the game to steal a resource. The attached screenshot shows an example of this situation, but it is easy to reproduce. I have not looked into what happens if there are two other players on the tile.