I think it may be a permissions problem. Are you sure that you can execute the file in /usr/sbin?
What are its permissions? Are you just at user level or "root" when you try to execute this command?
When I look at my own /usr/sbin, there are several files that don't have world executable set.
Also, it looks as though the second PATH at the bottom contains all of the directories that the first one has. I would comment out the first one with a # sign. Then log out and log back in. I think you would be better served by this.
In addition, I would take out the . after the $PATH: That can be a problem for security, but I don't think that is related to your problem.
Your problem is either a PATH problem or a permissions problem. Try that and let me know.
it looks like you have HPUX. Here are some alias commands that I have setup.
# list of my aliases
alias dir='ls -la'
alias lt='ls -lt'
alias lrt='ls -lrt'
alias pp='ps -aef|grep'
alias lsfg='lsf |grep '\/''
Hope this helps.