Hi Janne, have you possibly changed the display mesh setting to some very small angle value?

What do you have set under Options > View > Meshing parameters > "Mesh angle" ?

The default value for that display setting is 10 degrees - if you have set it to something smaller than that, it can cause MoI to make a very heavy display mesh and that can have some side effects like you are describing.

If you are working with complex scenes you may want to set that value to something more like 25 degrees to make a coarser looking but quicker to calculate display mesh.

- Michael