Hotmail rejected my email for policy reasons. Said there was a complaint... how can I resolve the problem?

Here was the message I received: "Remote host said: 550 SC-004 Mail rejected by Windows Live Hotmail for policy reasons. A block has been placed against your IP address because we have received complaints concerning mail coming from that IP address. If you are not an email/network admin please contact your " and it was blank... it didn't tell me who to contact or anything. I was just sending a 'hey how are you' to my cousin. I don't know why anyone would have filed a complaint against me anywhere... I don't use email that much to begin with, and then only with family and friends! I have good virus protection on my computer, so I don't think that my email was overtaken... but it may have been... please help!