It says "this file is unknown to the blacklist scan", I think it means that the file is totally new and was never scanned before on VT. It is too fresh to even have a VT score. That is the suspicious factor here, IMO.
Now it is much too late to test, but if it happens again, try this: upload the file to VT, wait until it gets scanned by all the engines, and then let voodooshield try again.
