Dear Maurizio,
We are progressing. When ::xowiki::Object is not defined, this is a sign of some earlier installation errors, which are most likely visible in the error log of the aolserver.
Check out the xowiki faqs, http://alice.wu-wien.ac.at:8000/xowiki-faq/#install-errors
There is a similar error to what you are describing.
most likely it helps to upgrade nscache to 1.5 via
cvs -z3 -d:pserver:mailto:anonymous@aolserver.cvs.sourceforge.net:/cvsroot/aolserver co nscache
