I'm not sure if this a problem in Newsbin 6.62 or some kind of file name obfuscation in the NZB file, but even though I only needed one block to repair the downloaded archive, Newsbin downloaded all the PAR files and couldn't repair the archive. When I looked in the download directory every PAR file had a different name. All I had to do to was open any one of them and it was able to repair the archive.
If this isn't a bug in Newsbin, can't you make Newsbin try a PAR file with a different name if they are all downloaded into the same directory named for the NZB and there is only one archive? It seems to be obvious, to me anyway, that the other PAR files belong to that archive, no matter what the file name is.