Karamba typical "Singular Stiffness-matrix: Can not solve static system." problem

Good morning (from Spain) people,

Well I have a really simple structure and I want to play a little and learn with Karamba. I get this message:

1. Singular Stiffness-matrix: Can not solve static system.
Make sure that boundary conditions are set so that the structure can not move in rigid body modes.
When you analyze a flat shell structure lock the rotation perpendicular to the plate in at least one node.
Use the 'Eigen Modes'-component and activate the display of local coordinate axes: The first eigenmode will be the rigid body motion.

and I have looked for another posts like this: 

http://www.grasshopper3d.com/group/karamba/forum/topics/analyse-wea...

http://www.grasshopper3d.com/forum/topics/karamba-user-problems?gro...

But I dont know how to solve my problem. I have 6 supports, all translation and rotation possibilities fixed. I have tried with Beam Joint and the Eigenmode command.

What should I do?

Best Regards, 

Daniel