> >If I type '-s' at the boot blocks, and press return for /bin/sh
> >when I reach the shell selection prompt, the machine pauses
> >then marches forward with /etc/rc like I as if I issued fastboot
> 
> Is there anything in /root/.profile that might make the shell exit?

No, but there was in /etc/profile.  I had forgotten that /bin/sh sources
it even for single user boot...