You are probably trying to renew a Dr.Web Security Space (Dr.Web Anti-virus) license, and purchased a Dr.Web box containing two serial numbers (or two licenses, each for one PC). When you were registering the first serial number from the box, you specified your old license’s serial number. As a result, you ended up with a new license whose term had 150 days added to it as a renewal bonus. Most likely, you tried to register the second serial number from the box and again specified the serial number from your old license. Since 150 days were already added to the term of your new license, Error 401 occurred when you tried to register the second serial number. Register the second serial number as a new license to which the renewal bonus does not apply.