Did Norton say it was a virus, or that it didn't know enough about the product? (I think that has reputation in the 'virus' name)

Some of the AV companies like to assume that if they know nothing about a file then it must be a virus and so scare the user.  This is a big problem for small software companies as Norton are in a position of trust with customers and so customers may wrongly assume the software vendor is shipping viruses.

Norton Internet Security reported that the threat, "WS.Reputation.1", is in the download for ModernMix 1.00.0; however, I assumed a false positive.  Restored the download from quarantine.  Malwarebytes, Panda Cloud Cleaner, and TrendMicro HouseCall all reported that the download file is clean. 

Completely disagree: Not only is that not the best advice, possibly not even good advice. Norton Internet Security is among the top three or five anti-malware products on the market. However I agree with Neil, in that it can be over zealous in its attempt to protect users from files not yet known or given the green light by its collective of users.

False positives can be reported; although it may take some time to be rectified. In the meantime a person can choose to un-quarantine MM and mark it as safe, and to be excluded from future scans.

regards,

Laurence