You mentioned something about setting the classpath. From my very limited experience it seems a wrong classpath makes for strange errors. I always set my path to look in the current directory (by adding .; --- classpath=.
I figure, I'm not sure if it's the best practice but it helps solve more problems than it creates. Try adding that, at the worse it will rule that out.
I noticed in your code (for DansUtil) above you had import chn.util.*; then you mentioned you compiled with
javac -classpath D:\junit3.8.1\chnutil.jar;. DansUtil.java
Did you mean chn.util with a period? I'm having a little trouble understanding if this is the same or not. Also wondering if the relationship between chn.util being imported and the class importing it. (Sorry if I'm leading you on wild goose chases).
Anyway, I recreated a similar (package) scenario on my system with very stripped down code and it's working fine.
I didn't put in any of the chn.util code so I'm guessing it has to do with that. Where is chn.util saved in relation to the other packages?