animation fundementals

Hi i have bought numerous lessons from CG cookie and am now working on animation fundermentals by Beorn Leonard.
I am having a few problems with my moving walk cycle. Beorn uses extrapolation modes in his graph editor but i am having major problems following him. I have got the walk cycle to move a few steps and then it just stops on the spot but continues to walk (not moving forward). Can anyone help me solve my problem please. I have watched the video over and over again and cant see where im going wrong.

I have been working on this little project for a hell of a while and DanPro suggested i get something down so i dont get so frustrated and give up. So walk cycle was my first try and low and behold i got stuck yet again.

Pleas please help

Many thanks

http://www.pasteall.org/blend/35723

here is the file to see if anyone can help me out.

I can not find any walking in the blend file.