Getting on an OFAC list is a nightmare for any business. It usually happens because of some accidental link to a sanctioned entity or just a mistake in identity. You have to file a petition for delisting and it requires a lot of technical paperwork. We had a similar scare and found useful info at www.humanrights-lawyer.com about unblocking assets. They know how to handle the administrative side of these sanctions. It is mostly about proving that you don't pose a threat and that the listing was a mistake. Be prepared that it takes time. The US Treasury is not known for being fast. You should definitely hire a professional who speaks their language to speed things up.