And yes, I've been restarting Processing. 

I don't know CSound and you don't give a link, but are you sure you import the right package from this jar? Just checking the only idea coming to my mind...

Well, I never did figure this one out. I suspect that the package name may differ from the name of the jar, or something like that. So it may very well be I was not importing the right package. I stopped investigating the problem as I'm now piecing together a proper Csound Library for Processing, side stepping the issue. So it's all good. 

I'm also having this issue.  Testing out using Gephi with Processing.  Works fine if I drag it into the Code directory.  Import statements all work fine.  But if I try to move it to libraries/gephi/library/gephi.jar, it's a no-go.  Can no longer find it.  Wanted to modify the examples and make a distro for Processing, but can't quite get it to work with the normal process.

Exported app (when the jar is in the code director) and looked at the source .java file and it uses the same import command that I'm using.  So it doesn't seem to be anything I have in the program.  It has to be something with the way the class is defined in the jar file...???