filesystem creation problem during the installation process.

[Jesus Romero]

Hi,

I have the following issue:

Once I've chosen in the sysinstall main menu:
1- Standart Installation
2- ad0 as selected drive.
3- I've deleted the current partitions there and created a new one for
Freebsd using "Use Entire Disk". But I have to click S to define this
slice as ACTIVE partition and that's it. Click Q.
4- I use "Fdisk Partition Using Entire Disk" I click "A" as default
partition. Click Q.
5- I select Standar like Boot Manager for drive ad0.
6- For Choose Distribution, I choose ALL.
7- For Choose Media, I choose CD/DVD.
8- And after I got the following warning:

 User Confirmation Requested
 Last Chance! Are you SURE you want to continue the installation? 
 If you're running this on a disk with data you wish to save then WE
 STRONGLY ENCOURAGE YOU TO MAKE PROPER BACKUPS before proceeding! 
 We can take no responsibility for lost disk contents!  
                             [ Yes ]    No

9- I chose, YES, and I've always gotten the following message.

[ Unable to find device node for /dev/ad0s1b in /dev
  Creation of filesystem will be aborted ]

10- I've tried a lot alternatives, but without luck!!

Please HELP!!!
Thanks Advanced!