OK. Thanks to the informative forum at HF-ALE, I have the intelligence that Windows 7 security prevents programs from modifying certain files in their own home folders and subdirectories therein. Variable data is supposed to be stored in User Data, App Data, or someplace like that. These old ham programs don't do that.
The advice was given to create a folder OUTSIDE Program Files (x86) for old radio software that won't work any other way, and install these old programs there. While they were talking about PC-ALE, this worked for DSCdecoder. The ITU lookup is now working and the program is as far as I'm concerned now operating properly. The display screen changes, and the data is written to the daily log and shipid.txt.
While I was at it, I moved the logging folder to My Documents, since I look at it a lot. This is done with Options > Directories > Log File.
I wouldn't recommend this installation procedure for every single new program, since it does defeat a security feature built into W7. This is for the care and feeding of these old radio sharewares. Make sure you trust the software.