IRCOps can k-line people, or it could be automatic from the network. Normally, your message will tell you why you were k-lined, even if the reason doesn't make sense to you. Sometimes, k-line bans are on the ISP itself, so it may have nothing to do with you. You may just be suffering the effects of someone else's ban.
You can always e-mail the network (most networks have a website with contact information) and ask what the k-line was for.
