I use the lastest beta 7.78.8085.
Create a new empty folder, create empty mirc.ini, drop the lastest beta exe in the folder and run.
The server list should be empty, but when I found this issue, I had connected to irc.swiftirc.net already so my server list has only swiftirc in it.
It's easier to test this by having a grouped nickserv nickname on the network you test on.
Enter a main nickname in Alt + o > connect (nickA)
edit the server entry you test this on (swiftirc for me)
Enter your password for the nickname and choose an appropriate login method supported by the server
Go to the nickname tab, check the box use nickname and enter a different nickname there (nickB).
Connect to the server any way you want, gui or /server.
mIRC may connect you using nickA, in this case, it won't try to log you in, this is the bug.
However mIRC may connect you using nickB, which is correct, in this case it mIRC will log you in correctly.
I only tested this a couple of time without being able identify why it's intermittent.
It's possible to run mIRC, connect and it will use nickB incorrectly, but doing a /server -m to that same network will correctly use nickA.
