I have the same problem, but only when I'm running something CPU intensive on the foreground. It is definitely a mIRC problem, possibly in co-operation with a new WinXP 'feature'
Personally what I think is happening is that mIRC is using an idle priority thread to maintain it's connection to the server (like responding to the pings with pongs) and that the thread is being 'starved'.
The odd thing is that it doesn't ALWAYS happen. Usually I can play my game fine and stay connected, but sometimes it has a bad day and I hear disconnect/connect dings every 5 minutes while playing. Usually it fixes itself if I just restart mIRC, but it's still annoying.
