i should add one more thing to clarify some of my suspicions: i'm a developer and have worked with winsock (wrote C++ interface that unifies socket access over unix and windows). i know that winsock is an horrific mess - nice idea, asynchronous socket event notification, however the implementation can only be described as "ad hoc." (about the worst insult i could think to level at a developer wink ) very few things work reliably, and retry logic is pretty dominant in any code that uses winsock. at one point i had to get some windows software working in kuala lumpur and spent most of my time tuning the winsock interface.
my point is, that maybe there is something about the internet in china (or in the specific locale concerned) that mirc isn't able to deal with at the winsock level? perhaps there is some configuration relating to this that i haven't found yet?