If I'm reading this correctly, this is happening:
1, You start mIRC and connect to ZNC. Everything is fine.
2, You lose connection to ZNC and this happens:
3, Then mIRC seems to get "confused" and something like this happens when it reconnects:
I've had this issue before when I used the servers.ini file. Basically mIRC seems to freak out when it loses connection and it tries to connect to the very first network in the treebar for ALL the connections.
I stopped using (I deleted mine, you might want to make a backup to save your info) the servers.ini (ALT+E). Now I just use an on start
script to connect to all the networks in the znc.