Your off topic if your talking about the OneCare Safety Scanner, since this forum deals with the OneCare by subscription application, but the usual way to test for false positives is to send any files identified as infected to the following sites for an analysis by 80 or so different Anti-malware engines, so there's a lot less probability of OneCare or Norton alone either confirming or missing any detection:
http://virscan.org/index.php
http://virusscan.jotti.org/
http://www.virustotal.com/
The Safety Scanner forums are here, where it would be helpful if you post your comparative results:
http://boards.live.com/safetyboards/forum.aspx?ForumID=13