Differences between the nla editor and action editor

Hi,

I want to make a walk cycle for my alien model. So I made the keyframes and after that I inserted the action into the NLA and converted them into a NLA strip. But the problem was that the feet slide on the ground.
To solve this problem I converted all the actions IPOs into linear interpolation. This solved the problem a little bit.

But now I have another problem. I noticed that the walk cycle is a little bit different in the action editor as in the NLA editor.
For example frame 1 in the action editor looks different than the frame 1 in the NLA editor. Also frame 6 looks different. Because of this the walk cycle produces a slight sliding effect. Why are there differences in the NLA and action editors?

Can someone please help me with this? All comments are welcomed.

frame 1 in the action editor:
http://toth.a15177265.alturo-server.de/blender/frame1_Action.png
frame 1 in the nla editor:
http://toth.a15177265.alturo-server.de/blender/frame1_NLA.png
frame 6 in the action editor:
http://toth.a15177265.alturo-server.de/blender/frame6_Action.png
frame 6 in the nla editor:
http://toth.a15177265.alturo-server.de/blender/frame6_NLA.png

You are not dealing with different types of data --just different ways of viewing and manipulating it. If you open the IPO Curve Editor you’ll see yet another view of the keys you inserted.

The Action Editor is used to define multiple, distinct actions: such as walking, running, jumping, etc.

The NLA Editor is where you can apply those actions in varying degrees. For example, you can start a walk action and blend it into a run action, repeat the run action a few times, blend it into a jump action and finish with the character simply landing and standing.

Hope this makes sense.