VirtualBox FreeBSD as guest

[Giulio Ferro]

Freebsd 8 last (yesterday)
When I try to launch it as a guest os in virtualbox during boot I get
a lot of:
ata0: timeout waiting to issue command
ata0: error issuing ATA PACKET command
...
...

Eventually it manages to complete boot and everything seems to work ok.
But when I try to mount cdrom (i.e. to install guest additions) :
mount_cd9660 /dev/acd0 /mnt/cdrom
It fails with the same errors reported above and finally:
mount_cd9660: /dev/acd0: Input/output error


Host system is ubuntu 10.04 amd64. Other o.s. works ok (7, xp, ...)

I've tried to change the controller type in the VB config, but nothing 
changes...

Thanks for any suggestions