When connecting to an unavailable and/or inexisting server, U61 might freeze. This is because the "connect" function (form the low-level communication layer) blocks and does not return until the server is found.
This is due to some inperfections in event handling. What happens is that the game core spends more time displaying things than processing events. Therefore there's a growing time gap between what's displayed and what's being calculated internally, at an event level. And the situation gets worse and worse as the display gets slower since the engine has to anticipate many frames. So the game chokes to death... I'm trying to find a compromise between real-time constraints and performance issues.
Well, this is I hope only a temporary behavior, which should be changed in the future. The point is that when a client connects itself on a server, it gets a whole history of what has been happening on the server, and it can take quite a time to process.