FreeBSD 8.0 failes to start

[Giorgos Tsiapaliokas]

hello my os fails to start,this is the error and also my keyboard doesn't
work

Root mount waiting for: usbus3

Trying to mount root from ufs:/dev/ad2s2a

ROOT MOUNT ERROR:

If you have invalid mount options, reboot, and first try the following
from the loader prompt:


     set vfs.root.mountfrom.options=rw

and then remove invalid mount options from /etc/fstab.
Loader variables:

vfs.root.mountfrom=ufs:/dev/ad0s2a

vfs.root.mountfrom.options=rw