CST - use of STL structures

Hello,
I tried several times (Had too) import STL files in CST rather than SAT.
I was never able to get it to run.
Anybody has any experience?
I get this message:
<<Preparation of the ACIS model failed. Disable PBA acceleration or use non_PEC Background material.>>
Any ideas?

stl? format what is it?

it's sheets, rather than solids

Hello,
what version of cst are you using? 2006B will handle sheet without converting to staircase mesh. In older version you will have to use staircase mesh for sheet objects if you are using Transient solver. Also check solve --> background material and make sure it is normal and not PEC.
Hope this helps.
Regards,
Element7k