Newsbin Pro 6.51 Build 3159. This used to happen periodically with previous builds but has become pretty consistent with 6.51.
What is happening is I select a bunch of files to download. Sometimes, they will show up in the download list and sometimes not. When the files do not show, they do download and I can see the data transfer with the speed progress indicator. The behavior is random. Often, I wait until every thing is downloaded, then I restart Newsbin. Sometimes, it will take two, even three restarts before files to be downloaded will show in the Download list.