Actually, the technical reasons related to undownloaded content when connecting has nothing to do with that, JelZe, though it is a good enough assumption to consider in any case. Here are the reason in order of occurrance.



1. The server you are connecting to missed a packet it tried to transfer when sending the server information. This occurs most often when the server is experiencing server-side laggy moments (i.e. 0 baud when many people are downloading and joining at the same time.)



2. The client's side is consistantly missing transmitted packets and is no longer sending packets of information to the provider. This is caused by peak times and service provider trips. This does not occur for high-end connections that aren't using dialup.



3. An error has disconnected the joining players pertaining to a serverlist's wavering. The latest error served on the serverlist can be easily found by telnetting the serverlist. This isn't too common as implied by the number of errors, but it is more prominent than most other reasons.



4. The server had shut down/restarted while you were downloading, and not connecting.



5. The serverlist had shutdown, which causes all the servers to collapse as a result and go solo on their own local list. Since the clients were routed through the serverlist and the connection disconnected from there, the clients must rejoin the locally represented server.



6. XJJ2 servers aren't very stable as JJ2 is being executed externally and many controllers are being skipped in activation as a result of external program execution. The server is prone to errors and disconnections because of this. Should you be hosting the default three gameplay modes, it is advised that you use JJ2 to do so.



7. Someone in the server is using an external program to entangle the server-wide program codes and use "laser shields". When laser shields are being used in a server (a rarity as the people who use them are rarely using them at all) they temporarily disable client connections half-way since the program is being infiltrated and the reaction of the program is filtering clients from getting a weak error naturally. On a side note, if Overlord's Anti-access Violation Patch works, you should apply it so you won't experience a long string of messages when they appear.



8. A strong firewall had somehow been activated after connection to the server. This is also a rarity.



That's all you may really watch out for (especially for dial-up users) aside from number eight, which is a very silly thing to think about. Whatever the case may be, there is no way to stop server-side/client-side problems as long as lag exists at all.