Well. No wonder it crashes. The size of the geometry is not 3 or 5 mts as you said. Just measured one of the boxes, while my units are set to meters, is more than 15000 mts!!!
You can work in whatever units you want butbe aware of that and set the grid size accordingly.
Check your geometry and be more careful with that.
-A.
Thanks Abraham. This worked bueatifully.
I guess the mistake was when I changed the model units from millimeters to meters!