The previously stated problem occurred immediately after upgrading to the 0.24.2 version of AltBinZ. The files were part of the download queue from the previous version (0.24.0 I beleive) which had been automatically carried over. I'm not sure if that is relevant or not.
The log file indicated the normal:
[time] [T1] Article started 1/1 FileName
[time] [T1] Article finished 1/1 FileName
However, upon the decode it gave the error:
[time] [Dec] No files found
[time] [Dec] Subject: Post_Subject_Name "FileName" yEnc
After closing AltBinZ, or after a successful "download queue autosaved" from the log, the files in the download queue could be downloaded again with no problem. They were not cleared from the queue after the initial unsuccessful attempt, nor did the download bar indicate anything but 0%.
As I mentioned before, I did not want to waste the bandwidth redownloading everything. It was all there in the AltBinZ temp directory. I was successful in the tediously manual process of decoding the individual parts with the utility from the yEnc website.