HEAD newfs/sysinstall issues

I've been trying to get the current HEAD snapshot installed on an  
amd64 box that had some screwed up disk geometry from a previous  
install.

When sysinstall runs newfs it complains that it's unable to locate  
the /dev/ad0x (replace x with whatever it was trying to newfs).  Seems  
like the partition does get created but does not become visible in /dev

7.X works fine.

Any ideas?

-B