This happens in a lot of places but I decided to demonstrate it with this dead brahmin and items that I happened to run across while I had the camera handy.

Video here: http://www.youtube.com/watch?v=yn4SgY20-6o

At the end I tried to drag the dead brahmin off of the items (Z key) before trying to pick them up but as soon as I hit the Z key they fell into the ground anyway.

I noticed the same thing, also I came across some places with floating rocks and other terrain stuff thats not on the ground. Some npc's, scorpions, centaurs etc stuck in the terrain with half of their body buried, they're unkillable since its like the bullets hit a invisible wall, explosives doesn't work either, had to open up console click on exposed part and type "kill" cause otherwise my companions would be stuck there trying to kill it forever.