No feedback for >1/2 year and I can't reproduce this issue with virtualbox 
2.2.2 and grml64 2009.10-rc1. Closing this issue therefor. Please reopen it if 
you still encounter problems on your setup.

regards,
-mika-

Alright, I can reproduce the bug if run 'grml-x -force fluxbox'. This recreates 
the xorg.conf and fails. If I use 'grml-x -force -module vboxvideo fluxbox' it 
works fine. We ship virtualbox-ose-guest-utils with grml[-medium] 2008.11 so I 
don't understand why it shouldn't work there, though this might be an issue on 
the 64bit version. Gebi, can you please investigate on that?

regards,
-mika-

the lastest grml rc (2008.11-rc1) gives only a black screen in virtualbox on
amd64 (both 32 and 64bit grml).

virtualbox version tested: both 1.6.6-dfsg-3 and 2.0.4-38406_Debian_lenny.