Cannot import xar file in empty xwiki running on standard tomcat5.5

When empty xwiki instance is created and xar file is imported, it does not work without any warning on tomcat5.5, from ubuntu 8.04 standard repository but work on tomcat6 from apache website.
To reproduce bug, set-up ubuntu 8.04 x86_64 server with tomcat5.5 from ubuntu repository (sudo apt-get install tomcat5.5) and tomcat 6.0.33 from apache http://tomcat.apache.org/download-60.cgi
Then try to import xar file. note, that in one case import simply doesn't do anything, but work on other.