Spybot (free version) and Malware bytes (premium) did not find anything. So I began to look elsewhere. I remembered that I had recently installed AVG Zen (paid version), so I wondered if there was a conflict somewhere with something else already installed.
Enter "Adfender." When I disabled it, I was able to use the upload feature here on TestMy.net. There had never been a problem before, so I am assuming there is some sort of conflict between Adfender and AVG.