You're right, I did have the CLASSPATH pointing to the folder, rather than to the .zip file.
So, here's what I did:
I removed the jr.zip file from the lib\ext folder, and pasted it to my c:\Program Files\Java folder. I did not unzip the file.
I then changed the CLASSPATH to "c:\Program Files\Java\jr.zip". Just to be sure, I restarted my machine.
I opened up BlueJ (My IDE of choice), wrote a stup program with a first line of "import com.javaranch.common.*; " and got the error message "package com.javaranch.common does not exist."
Next, since BlueJ is on my E: drive, I copied the jr.zip file to "E:\BlueJ\lib", and edited the CLASSPATH to "c:\Program Files\Java\jr.zip; E:\BlueJ\lib\jr.zip. I rebooted the machine, tried to compile my stub program --- same error message.
Finally I changed the CLASSPATH to "E:\BlueJ\lib\jr.zip", rebooted, recompiled, ... same thing.
I've always thought myself to be a reasonably intelligent person. What am I missing, here??
Thanks for the help thus far!