Forums mIRC Help Nickname allready in use

So I left mIRC open overnight while my computer was in sleep mode. This morning I took it out of sleep mode, to discover that mIRC had been closed. When I logged into the server I ussually log into, it told me my Nickname was allready in use.

upon doing /whois it showed my nickname as having just logged in. Because of the nature of what I'm doing on that server, it's important that I be able to log in as that same nickname.

Any ideas how I can force it to log off somehow?

If the nickname is still in use after about 5 minutes, then mIRC is probably still running. It doesn't just close anyway.
Check your systray (also any 'inactive' icons there which may have been hidden by Windows) to see if you find the mIRC icon there.

If it's not there, then you can also try reviewing the list of running processes in the Task Manager.

If the network supports nick registration, then register that nick.
The common, but not only, method of doing this is to use /msg nickserv register <password>

Some networks also require a valid e-mail address be supplied so that they can send you a verification e-mail, which will contain a special code.
This is, in theory, to ensure that the request is coming from a real person.

I recommend going to the networks help channel, usually #help, and talking to them to see what the method and details for registering the nick is.

Until the nick is registered, anyone can use it.
If the nick is in use by someone else, then you won't be able to register it until you are using the nick, and you also have to hope that someone else doesn't register it first.