mIRC is software used to IRC (internet relay chat) on any of many networks, which you get to by connecting to one of their servers. So no, miRC isnt down.
The error msg you got, "Unable to assign..." is because the server you tried to use isnt reachable by you or anyone else.
You are in the part of this message board for discussing Connection Issues. In the index for each area of this msg board, (you can click here to see what i mean by index:
click here ) you may see threads (this is a thread) that are always at the top, and never move downwards. Those are what we call "sticky posts". We keep them at the top of the forum because they are common issues/have info you should know.
You will see one called DALnet Active Servers in which you will see a link to a website that has been keeping track of what servers are linked to DALnet, if DALnet is the one you are having problems getting to. You are prolly getting this error because you are trying to connect to that networks "random" like irc.dal.net. It is called random because it isnt a server itself, it connects you to one of their servers (ie, a random one). The solution is to find out what servers are actively linked to that network, by going to the networks website for a list of them, or in the case of DALnet a link that a user has put up showing them. You can then, in mIRC, in your status window, type one of them. Examples would be /server irc.prison.net (which is an EFnet server) or /server mesra.kl.my.dal.net (one of DALnet's servers)