Starting new topic to take attention
http://hg.slitaz.org/slitaz-boot-scripts/rev/79aea3c677ca#l1.45
it was here
http://forum.slitaz.org/topic/error-loading-tazusb-writefs-gzip-generated-initrd-since-rc1-to-latest-june3rolling/page/2#post-30881
also, about virtualbox modules wrong path.