I reinstalled Jython using the

java jython-21

command in the directory into which the files were to go and mysteriously, I no longer get the numerous

    *sys-package-mgr*: can't write cache file
warning messages when I launch Jython.
Could this be because I originally ran the jython-21.class file in a different directory (from where the files ended up)? 
The registry and jython.bat files are identical to the previous versions.
Sorry to waste the list's time, but perhaps users may experience the same problem in future?