Problem writing to BUDA
libbluray creates this folder: .cache/bluray/bluray.bindingunit.root/ This is the BUDA folder that Xlets can write larger amounts of data to, typically as part of BD-Live when downloading extra bonus material etc. As far as I understand, each organisation gets their own folder in the BUDA folder, named with the orgID. This folder must be created by libbluray before Xlets can write to it. Currently no orgID folder is made, and therefor Xlets can't write to BUDA.
So it's an easy fix: Simply create the orgID folder in .cache/bluray/bluray.bindingunit.root/ when the disc or xlet starts.