First off, I'm using the Norton Security Suite that Comcast provides free for its customers. Offhand I'm not sure what version number it is, but it's the latest and completely up to date.
So I made an observation and posted it in the Comcast Security help forum and was told to come post it here. I'd link to it, but you'd have to be a Comcast customer in order to see it, so that probably won't help.
At any rate, I am pasting the contents of it in here, contents below:
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I was running a manual scan on a folder through the Windows right click context menu: Norton Security Suite>Scan Now...
It *looked* like it was doing its thing and I got a message that no viruses were detected. Good, right? Well, I would think so of course, but then I clicked on Details and under Total Items Scanned it said 0. As in zero, zip, nada.
Well, I guess if nothing in a folder is actually scanned, it's a pretty safe bet no viruses will be found. I could have had that folder filled with every virus known to man and Norton would have given the *false* message that all was well. 
First off now, I know what happened, so I'm not asking for help - I'm bringing this to everybody's attention in case they haven't yet noticed themselves:
I realized after a minute that the drive that that particular folder was on was one that I had added to the Scan Exclusions list, thinking WRONGLY that that meant it would ONLY be excluded from AUTOMATIC scans.
Truth is, if a drive or directory is excluded from scans, it is excluded, PERIOD, even from manual scans.
So instead of Norton simply giving me the statement that no viruses were found, what it SHOULD say is something like "No scan performed. Manual scan cannot be performed on an excluded directory."
Some may think, well duh, that's pretty obvious, but no it's not. When it takes a moment and looks for all intents and purposes to be scanning and then gives the message that no viruses were found, it leads you to believe that a scan WAS performed, but no, it wasn't.
Now I realize most people are probably not messing with their exclusions and are just leaving everything at default, but Norton needs to be aware that some of us out here do use those features and have good reasons for doing so. After all, they included the feature, so apparently they recognize that some people have a use for it.
Again, it really ought to tell you that no scan was performed, rather than allowing you to believe it was and all is well.
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So that is my suggestion - Please change this erroneous message from Norton regarding scans that don't actually happen...