You'll need to be careful to distinguish between motion blur and stutter.  If you see motion blur, look for this box in render settings and un-tick it.

If the individual rendered frames are *not* blurred, then look for unwanted keyframes:

P.S.:  I recommend that you render a series of individual frames in PNG format, then compose those in a video editor.  While Poser *can* output a video, if anything goes awry, you lose the entire animation.  If you render separate frames and suffer a crash, you still have whatever frames have rendered and can resume from there.  Also, you can adjust the compression *after* viewing the effect in a video editor.

Poser 12, in feet.  

OSes:  Win7Prox64, Win7Ultx64

Silo Pro 2.5.6 64bit, Vue Infinite 2014.7, Genetica 4.0 Studio, UV Mapper Pro, UV Layout Pro, PhotoImpact X3, GIF Animator 5