Couponbar

Every day, three or four times each day I get the "Threats Detected" window, with "Couponbar has been detected." message.

I've tried the "Fix" option and the "Exclude" option with no results. I suspect this warning is was created when I visited the Coupons.com web site.

Is this a valid threat and if not how do I stop Norton Security from detecting it as it (Norton) also changes my default web page in Internet Explorer?