The new beta has been uploaded. This fix required quite a few changes to related stable code.
mIRC determines the network name used in the log filename in several ways. First, there is the group name in the server list entry. Second, the network name specified in numeric 001. Third, the ircd version in numeric 004 (deprecated in the next beta). Fourth, in the network token in numeric 005. If no group/network name is found, mIRC creates log filenames without network names, eg. status.log as opposed to status.network.log. In cases where you open multiple status window that connect to the same network, these log files end up merged.
The group/network name is used in many features in mIRC. mIRC has to decide when to use the group name found in the servers list and when to use the network name determined at connect. For example, if you connect and then disconnect, current versions of mIRC revert to the using the group name for the status window (changed in the beta so that mIRC continues to use the network name until you initiate a new connection in that status window). The group/network name is used in many other routines, eg. to determine if any open channel windows are to be closed on connect, if you are connecting to a different network, and so on. So the order in which the group/network name is set/reset is important.
As the code had been stable for some time, the new changes may have side-effects and will need testing. Please let me know how they work out for you.