As stated in the title i have a problem with static simulation in SolidWorks 2011. I'm doing this for an assignement (I'm a student). This is a frame for an agricultural device, made out of two rectangular and two circular beams and sheet metal. I made midsurfaces for all the parts and deleted the bodys. In the Study i defined shells from midsurfaces. I am able to mesh the assembly, i also defined the material (alloy steel) but when i try to run a basic load and fixture example it plots a warning: "Material not specified to one or more shells". I have no idea what is the case with this as all the parts have material defined in the simulation tree.

I also attached the assembly in this post. I hope someone has the solution because this is pretty important to me.