tedster - 10:26 pm on Nov 23, 2010 (gmt 0)
It still looks like some kind of non-Google widget to me - one that is keying off the referer string to create an ad. And that's exactly what that box is... an ad trying to draw your click.
But more than that, it looks like possibly some kind of adware installed on your computer. I've used your exact search phrase [intellisw barcod scanner for mac] and done the click in IE8 and Firefox. I don't get the pop-up.
I think your computer may be infected with adware. And then the Google little Google logo would be an illegal ripoff.