"Set account Information

Hi all, first time poster (newbie). I have NIS 2011,version 18.06......, Vista,  IE8,  very happy with it all. I had NIS  set on a daily full scan until a week ago when it stopped scanning, now have to do  manual scans. I tried to set the Custom scan, scan schedule and up pops a "Set account information" asking for a password . I don't have a password for my computer, never have, my NIS used to scan on schedule, never missed a day, not anymore. I did a web check on the subject and found a million different answers. Any clues on how to get my scheduled scans back on track without this annoying "Pop up box" and a password that doesn't exist. TIA