First off, I'm hoping that this is a typo, since you say you just got the latest version of mIRC 6.12, and, in fact, the latest version is 6.21.
If you did indeed download 6.12, then it is not the latest version.
As to your disconnects, it would help if you could post the disconnect notice that is sent to your status window from the server when you are disconnected.
If it shows a message with the number 10053, then there is a very long topic about that
here 
