I get the following error when launching Eclipse:
*sys-package-mgr*: can't create package cache dir, '/path/to/Eclipse/install/.../plugins/org.python.pydev.jython_1.3.15/cachedir/packages'
The install directory is shared between multiple users, readonly, and the shared configuration is initialised at beginning of time. (See: http://help.eclipse.org/help32/index.jsp?topic=/org.eclipse.platform.doc.isv/reference/misc/multi_user_installs.html\)
It would seem to me that any global caching jython needs, should occur during the first initialise. And subsequently global settings should be stored in the user's personal configuration / workspace.