Problems with 3D contact/contact status

hi all,

I have some problems with contact elements in ANSYS.

My model is a cube of matrx containing two fibres with periodic boundary conditions. The interface between Matrix and Fibre is modeled with contact elements and cohesive zone law. 

In 2-D everything works out just fine when bringing up displacement in x-direction. Here is a movie I made of the Contact Status over the loadsteps:

http://dl.dropbox.com/u/4920002/2D_contactmovie_ContaStat_0.4.avi

Doing the same in 3D brings up some problems. The Contact status is not behaving as expected.

 http://dl.dropbox.com/u/4920002/3D_contactmovie_contstat.avi

Any ideas what is going wrong in the 3D case?

Thanks,

Andy