Version 3.0.6 is out for virtualbox and seems to fix some problems introduced in 3.0.4, which occured for those who used a virtual SATA controller (bugs #4695, #4739, #4710). Reproducible: Always Steps to Reproduce:
website of virtualbox does not seem up-to-date, but the changelog already contains version 3.0.6 and the BUGs, which were closed. http://www.virtualbox.org/wiki/Changelog
ebuilds bumped and available at jokey's overlay[1] [1] http://overlays.gentoo.org/dev/jokey
... and in tree. Thanks!