I have an assembly that all of a sudden started zooming way out when I click the isometric view or try to rotate the whole model. It zooms so far out that I cannot even see the model anymore. I can zoom back in to where I can see it again but the moment I try to rotate it, the model disappears again. It started happening just after I added and then deleted a couple of conflicting mates. Anyone seen this before and know what to do about it?