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.
You might get this message if you run U61 in windowed mode under Windows and close the application by clicking the standard "cross" which is in the top-right corner of the window.
If you compile the game with the "official" ClanLib-0.5.0 release, you might be unable to start network games under GNU/Linux, with the server complaining that it can't bind itself correctly. This is due to a very minor bug in ClanLib which has been corrected now, however you shouldn't use CVS snapshots of ClanLib to compile U61. Instead, you should use my home made www.ufoot.org/archive/ClanLib-0.5.0-for-u61-1.0.0.tar.gz release of ClanLib, which is slightly modified so that this bug does not occur anymore.
Due to some limitations in key handling in ClanLib, you might get trouble trying to type characters such as "." or "-". This is very annoying since you need them to type ip addresses and/or machine names. Still, there's a workaround for ".", which is usually the most annoying character: simply press the space bar on your keyboard and it will enter "." instead of " " if you are editing a server name.
Again, this is due to the fact that ClanLib is still under heavy developpement. I'll try and do my best so that this bug is fixed some day, since it is very important for U61 that all the keys work correctly.