Unable to find device node for /dev/ad4s1b in /dev !

Hi all:

Issue faced
 Installer on 'Commit' step shows
  Unable to find device node for /dev/ad4s1b in /dev!
  The creation of filesystems will be aborted.

System
 Intel Celeron M 1.6 GHz 
 Intel 945GM board
 2GB DDR2
 160GB SATA Seagate HDD

i'm using FreeBSD 8.0 200905 i386 DVD to try and install 
the OS.

Using the FreeBSD 7.1 DVD, i'm able to make the partition,
define the slices and install a 'minimal' distribution set.

However with FreeBSD 8.0 200905 snapshot i'm getting the 
above mentioned error.

Any pointers or workarounds ?


thanks
Saifi.