Have you made sure that your $PATH variable is set?
You can check by typing this in the Terminal:
echo $PATH
If nothing is listed after you try that... it might be part of the problem.
(For more information, you could try checking this page out: http://www.cyberciti.biz/faq/linux-unix-command-not-found-error-and-how-to-get-rid-of-it/)
