Thanks, I was able to reproduce this issue. The logging method has worked this way for a long time as there were side-effects with resolving it.

I can change the logging method so that if you are connected to network A, and you /server to network B in the same status window, mIRC will close the log file for network A, open a new log file for network B, and then connect to network B. However, this will result in the following side-effect:

If you have an alias that /echos out connection details regarding network B to the status window before calling the /server command, all those connection details will remain in the log file for network A. For example:

test {
echo Initiating connection to network $1
echo You last connected to network $1 on ...
echo Your current settings for network $1 are ...
server $1
}

In the above case, the first three /echos will remain in the log file for network A as that was the active connection in the status window at the time of the /echos. As the logging method has always worked the way it currently does, this will affect all existing scripts that depend on the current behaviour. On the other hand, the logging issue you describe will be fixed. If no one has any objections to or sees any other issues with this change, I will implement it in the next beta.