Computer suspended by internet service company?!?

[Rave]

We use Knology and I was just on facebook and then my screen went away and I got a notice telling me that I had committed illegal acts on my computer and that Knology had suspended my computer. I'm utterly confused because the supposed charges are things I didn't do and wouldn't know how to go about doing. It's only on my computer! And the company hasn't called or anything. The screen keeps telling me I have to pay a fine of $300 through moneypak within 48 hrs, or they will tell the police and totally delete everything off my computer! I'm really confused because it seems like a virus, but I've never seen one do this before! Normally I wouldn't be worried because I haven't done anything but my brothers occassionally use my computer and they might have done something. I want to tell my dad but I'd rather not if I can help it. Please someone tell me if this is just a nasty virus?! I can't get past it it pops up no matter if I restart or not. I'm really stressed over this! Someone please help!