A couple years ago I purchased a KitchenAid Blender. About a month ago
its started acting funny; instead of a constant spin the motor was
revving up and down. If you opened the small pour cap the liquid would
shoot out and hit the ceiling. Also whatever you were blending ended
up all of the top of the blender.

I went to Williams Sonoma to purchase a new one and explained my story.
They said I could return the blender for a new one so I swapped it out
for a new KitchenAid Ultra Power Blender.(Model KSB5WW4). I used it
for the first time today and had the same problem (different recipe).

At first I thought it may because the sauce I was blending was somewhat
hot (even though I blended many warm sauces with the old one before it
acted up). So I filled it with cold water and it still did not spin
constant.

Am I doing something wrong?
Has anyone had this problem with a Kitchen Aid Blender?

Thanks
Jeff