Poser going crazy between keyframes

I will make keyframe 2 a leg moved up..that it
I will make keyframe 30 the same thing, i dont change a thing
Yet when I scroll between 2 and 30 the leg spins around and goes crazy before returning to its right position in keyframe 30..what am i doing wrong?

Easiest way I found, is copy frame 2 and repeat it a few times (copy to frame 3, 4) and see if that is stable enough...but would love to see a better fix..

like delete hip/body frame or something..

I found the solution in a few earlier posts..shame on me for not looking first. HERE IS WHAT YOU DO GUYS: keep frame one the default pose, then on frame two go into the keyframe editor, select all the green boxes for frame two, and click BREAK SPINE on the top right corner, its a broken line button. This fixes the problem..and makes you feel good since ive wanted to break the spine on this stupid model for hours now since it wouldnt work.
Solution was provided by Siggy Romulus in little mings post! THANKS!

I had a similar problem where my model would dive off into oblivion before returning eventually to the second keyframe. The problem is the first frame, the default setup frame that Second Life requires you to have. When poser interpolates to the second frame (the first REAL frame of the animation) it does some crazy movement to get there, and then continues it to the next keyframe.

I fixed it by selecting the first two frames in the keyframe editor (all the green boxes on the two columns at far left) and setting interpolation to "Constant". It basically does the same thing as breaking the spline, in that it tells Poser not to execute interpolation from one pose to the next.