Similar to the Cone of Silence, the Cone of Ignorance is a state which can be said to have decended on a person, group of persons or project where by rational explaination is rendered ineffective.

Example, I was trying to explain why to our Pointy Haired Bosses why we couldnt run install Windows 2k on our spare Sun Microsystems E450, but the Cone of Ignorance had decended and it was no use.