can't run /sbin commands

[Dave Webster]

When I first installed FreeBSD I was able to run "halt" and "reboot" as
su without the full /sbin/reboot command.  After adding a new path to
PATH, I've been unable to run these commands without specifying the full
path.  
Recently I tried to install acroread 7.0 and the installation complained
I didn't have Linux ABI enabled.  When I check /etc/rc.conf, I have:
linux_enable="YES"
I noticed that when the system was trying to make install the acroread
port, it issued the kldstat command - then gave me the error about not
having linux ABI.  kldstat can only run if the full path /sbin/kldstat
is invoked.
Here is the output of echo $PATH:
/sbin:/bin:/usr/sbin:/usr/bin:/usr/games:/usr/local/sbin:/usr/local/bin:
/usr/X11R6/bin:/home/Dave/bin:/usr/home/Dave/apache-forrest-0.7/bin

My question is with /sbin in the path why do I have to
specify /sbin/reboot, /sbin/kldstat etc.?  Could this be causing my make
install to fail?  How can /sbin be in the path and still require a full
path declaration for it's commands to work.

regards,
Dave